chromium/src/third_party/blink/web_tests/http/tests/media/media-source/mediasource-htmlmediaelement-lifetime.html - manifest_repos/chromium_src - Git at Google

 <!DOCTYPE html>
 <title>Tests that GC preserves all of attached HTMLMediaElement+MSE when only part of that has a live reference.</title>
 <script src="/w3c/resources/testharness.js"></script>
 <script src="/w3c/resources/testharnessreport.js"></script>
 <script>

 function TestScope() {
     this.video = null;
     this.media_source = null;
     this.object_url = null;
     this.source_buffer_list = null;
     this.expect_durationchange = false;
     this.expect_sourceclose = false;
     this.received_sourceclose = false;
     this.expect_error = false;
     this.received_error = false;
 }

 function setup_htmlme_mse_lifetime_test(test, test_scope, handler_setup_cb, setup_done_cb) {
     // |handler_setup_cb|, if not null, is synchronously called after
     // test_scope is populated with HTMLME and MSE references, but prior to
     // attaching HTMLME to MSE API.
     //
     // Next, attaches the HTMLME to the MediaSource object and sets a timeout to later
     // call |setup_done_cb| so that hopefully any pending events or other work
     // are complete before the main part of the test proceeds.

     test_scope.video = document.createElement("video");
     test_scope.media_source = new MediaSource();
     test_scope.object_url = URL.createObjectURL(test_scope.media_source);
     if (handler_setup_cb != null)
         handler_setup_cb();

     test_scope.media_source.onsourceopen = test.step_func(function() {
         test_scope.media_source.onsourceopen = null;
         URL.revokeObjectURL(test_scope.object_url);
         setTimeout(setup_done_cb, 0);
     });

     test_scope.video.src = test_scope.object_url;
 }

 async_test(function(test) {
     var test_scope = new TestScope();

     var handler_setup_cb = null;

     var setup_done_cb = test.step_func(function() {
         test_scope.video = null;
         // |test_scope.media_source| should be the only remaining reference to HTMLME+MSE.
         // GC shouldn't collect HTMLME+MSE due to that live reference.
         assert_equals(test_scope.media_source.readyState, "open", "MediaSource object is open before gc().");

         // Debug note: setting test_scope.media_source to null here, and commenting out the assert_equals()
         // and test.done() lines, below, demonstrates with debug logging that HTMLME+MSE is collected, followed
         // eventually by a timeout.
         gc();

         assert_equals(test_scope.media_source.readyState, "open", "MediaSource object is open after gc().");
         test.done();
     });

     setup_htmlme_mse_lifetime_test(test, test_scope, handler_setup_cb, setup_done_cb)
 }, "GC of HTMLME+MediaSource preserves at least MediaSource when only the MediaSource reference is held by JS");

 async_test(function(test) {
     // This test builds on the previous test. It should fail if the previous test fails.

     var test_scope = new TestScope();

     var handler_setup_cb = test.step_func(function() {
         test_scope.video.ondurationchange = test.step_func(function() {
             assert_true(test_scope.expect_durationchange, "HTMLME durationchange event is expected only after changing MediaSource duration");
             test.done();
         });
     });

     var setup_done_cb = test.step_func(function() {
         test_scope.video = null;
         // |test_scope.media_source| should be the only remaining reference to HTMLME+MSE.
         // GC shouldn't collect HTMLME+MSE due to that live reference.
         assert_equals(test_scope.media_source.readyState, "open", "MediaSource object is open before gc().");
         gc();
         assert_equals(test_scope.media_source.readyState, "open", "MediaSource object is open after gc().");

         // Verify that HTMLME is still alive by changing the MediaSource object's duration, which causes
         // a durationchange event to become queued for dispatch on the attached HTMLME (and such dispatch ends this
         // test.)
         // Debug note: commenting out the next line should result in test timeout.
         test_scope.media_source.duration = 100;
         test_scope.expect_durationchange = true;
     });

     setup_htmlme_mse_lifetime_test(test, test_scope, handler_setup_cb, setup_done_cb)
 }, "GC of HTMLME+MediaSource preserves at least MediaSource and HTMLME when only the MediaSource reference is held by JS");

 async_test(function(test) {
     // This test builds on the previous two tests. It should fail if either of the previous two tests fails.

     var test_scope = new TestScope();

     var handler_setup_cb = test.step_func(function() {
         test_scope.video.ondurationchange = test.step_func(function(e) {
             assert_true(test_scope.expect_durationchange, "HTMLME durationchange event is expected only after changing MediaSource duration");
             assert_equals(e.target.custom_test_wrapper_update, "testing", "HTMLME wrapper, as adjusted by the test, should be retained");
             test.done();
         });
     });

     var setup_done_cb = test.step_func(function() {
         // Update the HTMLME JS wrapper with a custom property to be verified later.
         test_scope.video.custom_test_wrapper_update = "testing";
         test_scope.video = null;
         // |test_scope.media_source| should be the only remaining reference to HTMLME+MSE.
         // GC shouldn't collect HTMLME+MSE due to that live reference.
         assert_equals(test_scope.media_source.readyState, "open", "MediaSource object is open before gc().");
         gc();
         assert_equals(test_scope.media_source.readyState, "open", "MediaSource object is open after gc().");

         // Verify that HTMLME is still alive by changing the MediaSource object's duration, which causes
         // a durationchange event to become queued for dispatch on the attached HTMLME (and such dispatch ends this
         // test.)
         // Debug note: commenting out the next line demonstrates with debug logging that HTMLME+MSE is collected,
         // followed eventually by a timeout.
         test_scope.media_source.duration = 100;

         test_scope.expect_durationchange = true;
         test_scope.media_source = null;
         gc();
     });

     setup_htmlme_mse_lifetime_test(test, test_scope, handler_setup_cb, setup_done_cb)
 }, "GC of HTMLME+MediaSource preserves at least HTMLME and its wrapper when no references held by JS, but there is a pending HTMLME event");

 async_test(function(test) {
     var test_scope = new TestScope();

     var handler_setup_cb = null;

     var setup_done_cb = test.step_func(function() {
         assert_equals(test_scope.media_source.readyState, "open", "MediaSource object is open before gc().");
         test_scope.media_source = null;
         assert_equals(test_scope.video.src, test_scope.object_url, "HTMLME src attribute is correct before gc().");
         // |test_scope.video| should be the only remaining reference to HTMLME+MSE.
         // GC shouldn't collect HTMLME+MSE due to that live reference.

         // Debug note: setting test_scope.video to null here, and commenting out the assert_equals()
         // and test.done() lines, below, demonstrates with debug logging that HTMLME+MSE is collected, followed
         // eventually by a timeout.
         gc();

         assert_equals(test_scope.video.src, test_scope.object_url, "HTMLME src attribute is correct after gc().");
         test.done();
     });

     setup_htmlme_mse_lifetime_test(test, test_scope, handler_setup_cb, setup_done_cb)
 }, "GC of HTMLME+MediaSource preserves at least HTMLME when only the HTMLME reference is held by JS");

 async_test(function(test) {
     // This test builds on the previous test. It should fail if the previous test fails.

     var test_scope = new TestScope();

     var handler_setup_cb = test.step_func(function() {
         test_scope.media_source.onsourceclose = test.step_func(function() {
             assert_true(test_scope.expect_sourceclose, "MediaSource sourceclose event is expected only after clearing HTMLME src attribute");
             // Both HTMLME.onerror and MediaSource.onsourceclose are required to finish this test.
             if (test_scope.received_error)
                test.done();
             test_scope.received_sourceclose = true;
             test_scope.expect_sourceclose = false;  // Only one sourceclose is expected.
         });

         test_scope.video.onerror = test.step_func(function() {
             assert_true(test_scope.expect_error, "HTMLME error event is expected only after clearing HTMLME src attribute");
             // Both HTMLME.onerror and MediaSource.onsourceclose are required to finish this test.
             if (test_scope.received_sourceclose)
                test.done();
             test_scope.received_error = true;
             test_scope.expect_error = false;  // Only one error is expected.
         });
     });

     var setup_done_cb = test.step_func(function() {
         assert_equals(test_scope.media_source.readyState, "open", "MediaSource object is open before gc().");
         test_scope.media_source = null;
         assert_equals(test_scope.video.src, test_scope.object_url, "HTMLME src attribute is correct before gc().");
         // |test_scope.video| should be the only remaining reference to HTMLME+MSE.
         // GC shouldn't collect HTMLME+MSE due to that live reference.

         gc();

         assert_equals(test_scope.video.src, test_scope.object_url, "HTMLME src attribute is correct after gc().");

         // Verify that MediaSource is still alive by clearing the HTMLME object's src attribute, which causes a
         // sourceclose event to become queued for dispatch on the previously attached MediaSource and an error
         // event to become queued for dispatch on the HTMLME object (and such dispatches end this test.)
         // Debug note: commenting out the next line should result in test timeout.
         test_scope.video.src = "";
         test_scope.expect_sourceclose = true;
         test_scope.expect_error = true;
     });

     setup_htmlme_mse_lifetime_test(test, test_scope, handler_setup_cb, setup_done_cb)
 }, "GC of HTMLME+MediaSource preserves at least MediaSource and HTMLME when only the HTMLME reference is held by JS");

 async_test(function(test) {
     // This test builds on the previous two tests. It should fail if either of the previous two tests fails.

     var test_scope = new TestScope();

     var handler_setup_cb = test.step_func(function() {
         test_scope.media_source.onsourceclose = test.step_func(function(e) {
             assert_true(test_scope.expect_sourceclose, "MediaSource sourceclose event is expected only after clearing HTMLME src attribute");
             assert_equals(e.target.custom_test_wrapper_update, "testing-mediasource", "MediaSource wrapper, as adjusted by the test, should be retained");
             // Both HTMLME.onerror and MediaSource.onsourceclose are required to finish this test.
             if (test_scope.received_error)
                test.done();
             test_scope.received_sourceclose = true;
             test_scope.expect_sourceclose = false;  // Only one sourceclose is expected.
         });

         test_scope.video.onerror = test.step_func(function(e) {
             assert_true(test_scope.expect_error, "HTMLME error event is expected only after clearing HTMLME src attribute");
             assert_equals(e.target.custom_test_wrapper_update, "testing-htmlme", "HTMLME wrapper, as adjusted by the test, should be retained");
             // Both HTMLME.onerror and MediaSource.onsourceclose are required to finish this test.
             if (test_scope.received_sourceclose)
                test.done();
             test_scope.received_error = true;
             test_scope.expect_error = false;  // Only one error is expected.
         });
     });

     var setup_done_cb = test.step_func(function() {
         // Update the HTMLME and MediaSource JS wrappers with custom properties to be verified later.
         test_scope.video.custom_test_wrapper_update = "testing-htmlme";
         test_scope.media_source.custom_test_wrapper_update = "testing-mediasource";

         assert_equals(test_scope.media_source.readyState, "open", "MediaSource object is open before gc().");
         test_scope.media_source = null;
         assert_equals(test_scope.video.src, test_scope.object_url, "HTMLME src attribute is correct before gc().");
         // |test_scope.video| should be the only remaining reference to HTMLME+MSE.
         // GC shouldn't collect HTMLME+MSE due to that live reference.

         gc();

         assert_equals(test_scope.video.src, test_scope.object_url, "HTMLME src attribute is correct after gc().");

         // Verify that MediaSource is still alive by clearing the HTMLME object's src attribute, which causes a
         // sourceclose event to become queued for dispatch on the previously attached MediaSource and an error
         // event to become queued for dispatch on the HTMLME object (and such dispatches end this test.)
         // Debug note: commenting out the next line demonstrates with debug logging that HTMLME+MSE is collected,
         // followed eventually by a timeout.
         test_scope.video.src = "";

         test_scope.expect_sourceclose = true;
         test_scope.expect_error = true;
         test_scope.video = null;
         gc();
     });

     setup_htmlme_mse_lifetime_test(test, test_scope, handler_setup_cb, setup_done_cb)
 }, "GC of HTMLME+MediaSource preserves at least MediaSource and HTMLME and their wrappers when no references held by JS, but there is a pending event on each of HTMLME and MediaSource");

 async_test(function(test) {
     var test_scope = new TestScope();

     var handler_setup_cb = null;

     var setup_done_cb = test.step_func(function() {
         var source_buffer = test_scope.media_source.addSourceBuffer('video/webm; codecs="vp8"');
         test_scope.source_buffer_list = test_scope.media_source.sourceBuffers;
         source_buffer.custom_test_wrapper_update = "testing-sourcebuffer";
         assert_true(source_buffer === test_scope.source_buffer_list[0]);

         assert_equals(test_scope.media_source.readyState, "open", "MediaSource object is open before gc().");
         assert_equals(test_scope.video.src, test_scope.object_url, "HTMLME src attribute is correct before gc().");

         source_buffer = null;
         test_scope.media_source = null;
         test_scope.video = null;


         // |test_scope.source_buffer_list| should be the only remaining reference to HTMLME+MSE+SBL+SB.
         // GC shouldn't collected this group due to that live reference.

         // Debug note: setting test_scope.source_buffer_list to null here, and commenting out the assert_equals()
         // and test.done() lines, below, demonstrates with debug logging that HTMLME+MSE is collected, followed
         // eventually by a timeout.
         gc();

         assert_equals(test_scope.source_buffer_list.length, 1, "SBL should survive gc().");
         assert_equals(test_scope.source_buffer_list[0].custom_test_wrapper_update, "testing-sourcebuffer", "SBL[0]'s wrapper should survive gc().");
         test.done();
     });

     setup_htmlme_mse_lifetime_test(test, test_scope, handler_setup_cb, setup_done_cb)
 }, "GC of HTMLME+MediaSource+SBL+SB preserves at least SBL+SB when only the SourceBufferList reference is held by JS");

 // TODO(wolenetz): Consider further refactoring to extract specific testing concerns from the following test:
 async_test(function(test) {
     var video = document.createElement("video");
     var media_source = new MediaSource();
     var object_url = URL.createObjectURL(media_source);
     var malformed_media_append_started = false;

     video.onerror = test.step_func(function() {
         assert_true(malformed_media_append_started, "error should occur after append of malformed media bytestream started");
         test.done();
     });

     media_source.onsourceopen = test.step_func(function() {
         URL.revokeObjectURL(object_url);
         var source_buffer = media_source.addSourceBuffer('video/webm; codecs="vp8"');
         var source_buffer_list = media_source.sourceBuffers;
         assert_true(source_buffer === source_buffer_list[0]);
         source_buffer = null;
         media_source = null;
         video = null;
         // source_buffer_list's reference by us is the only thing keeping HTMLME+MSE alive.
         gc();

         setTimeout(test.step_func(function() {
             gc();
             source_buffer_list[0].onupdatestart = test.step_func(function() { malformed_media_append_started = true; });

             // Begin asynchronous append of a malformed media bytestream which
             // should result eventually with HTMLME error event firing due to the MSE
             // Append Error Algorithm.
             source_buffer_list[0].appendBuffer(new Uint8Array(10));

             // There should be a pending updatestart event on the SourceBuffer, so even if we drop the reference
             // to the SourceBufferList here, gc() still shouldn't collect HTMLME+MSE due to pending event dispatch
             // on MSE.  This is verified by HTMLME eventually handling an error event due to the asynchronous append
             // of malformed media.
             source_buffer_list = null;
             gc();
         }), 0);
     });

     video.src = object_url;

     // Debugging notes: If this test times out, it's likely due to failure in
     // keeping HTMLME+MSE alive and pending event dispatch on their wrappers alive
     // through gc(); either gc() over-collected HTMLME+MSE or event dispatch was
     // perturbed by gc().
     // If the assert in video.onerror fails, it is self-explanatory.
 }, "GC of HTMLME+MediaSource+SBL+SB preserves all when only SourceBufferList reference is alive, then SourceBuffer.onupdatestart and HTMLME.onerror are dispatched if they became pending during the asynchronous buffer append algorithm, of malformed bytestream, after all HTMLME+MSE references dropped");

 </script>
	<!DOCTYPE html>
	<title>Tests that GC preserves all of attached HTMLMediaElement+MSE when only part of that has a live reference.</title>
	<script src="/w3c/resources/testharness.js"></script>
	<script src="/w3c/resources/testharnessreport.js"></script>
	<script>

	function TestScope() {
	this.video = null;
	this.media_source = null;
	this.object_url = null;
	this.source_buffer_list = null;
	this.expect_durationchange = false;
	this.expect_sourceclose = false;
	this.received_sourceclose = false;
	this.expect_error = false;
	this.received_error = false;
	}

	function setup_htmlme_mse_lifetime_test(test, test_scope, handler_setup_cb, setup_done_cb) {
	// \|handler_setup_cb\|, if not null, is synchronously called after
	// test_scope is populated with HTMLME and MSE references, but prior to
	// attaching HTMLME to MSE API.
	//
	// Next, attaches the HTMLME to the MediaSource object and sets a timeout to later
	// call \|setup_done_cb\| so that hopefully any pending events or other work
	// are complete before the main part of the test proceeds.

	test_scope.video = document.createElement("video");
	test_scope.media_source = new MediaSource();
	test_scope.object_url = URL.createObjectURL(test_scope.media_source);
	if (handler_setup_cb != null)
	handler_setup_cb();

	test_scope.media_source.onsourceopen = test.step_func(function() {
	test_scope.media_source.onsourceopen = null;
	URL.revokeObjectURL(test_scope.object_url);
	setTimeout(setup_done_cb, 0);
	});

	test_scope.video.src = test_scope.object_url;
	}

	async_test(function(test) {
	var test_scope = new TestScope();

	var handler_setup_cb = null;

	var setup_done_cb = test.step_func(function() {
	test_scope.video = null;
	// \|test_scope.media_source\| should be the only remaining reference to HTMLME+MSE.
	// GC shouldn't collect HTMLME+MSE due to that live reference.
	assert_equals(test_scope.media_source.readyState, "open", "MediaSource object is open before gc().");

	// Debug note: setting test_scope.media_source to null here, and commenting out the assert_equals()
	// and test.done() lines, below, demonstrates with debug logging that HTMLME+MSE is collected, followed
	// eventually by a timeout.
	gc();

	assert_equals(test_scope.media_source.readyState, "open", "MediaSource object is open after gc().");
	test.done();
	});

	setup_htmlme_mse_lifetime_test(test, test_scope, handler_setup_cb, setup_done_cb)
	}, "GC of HTMLME+MediaSource preserves at least MediaSource when only the MediaSource reference is held by JS");

	async_test(function(test) {
	// This test builds on the previous test. It should fail if the previous test fails.

	var test_scope = new TestScope();

	var handler_setup_cb = test.step_func(function() {
	test_scope.video.ondurationchange = test.step_func(function() {
	assert_true(test_scope.expect_durationchange, "HTMLME durationchange event is expected only after changing MediaSource duration");
	test.done();
	});
	});

	var setup_done_cb = test.step_func(function() {
	test_scope.video = null;
	// \|test_scope.media_source\| should be the only remaining reference to HTMLME+MSE.
	// GC shouldn't collect HTMLME+MSE due to that live reference.
	assert_equals(test_scope.media_source.readyState, "open", "MediaSource object is open before gc().");
	gc();
	assert_equals(test_scope.media_source.readyState, "open", "MediaSource object is open after gc().");

	// Verify that HTMLME is still alive by changing the MediaSource object's duration, which causes
	// a durationchange event to become queued for dispatch on the attached HTMLME (and such dispatch ends this
	// test.)
	// Debug note: commenting out the next line should result in test timeout.
	test_scope.media_source.duration = 100;
	test_scope.expect_durationchange = true;
	});

	setup_htmlme_mse_lifetime_test(test, test_scope, handler_setup_cb, setup_done_cb)
	}, "GC of HTMLME+MediaSource preserves at least MediaSource and HTMLME when only the MediaSource reference is held by JS");

	async_test(function(test) {
	// This test builds on the previous two tests. It should fail if either of the previous two tests fails.

	var test_scope = new TestScope();

	var handler_setup_cb = test.step_func(function() {
	test_scope.video.ondurationchange = test.step_func(function(e) {
	assert_true(test_scope.expect_durationchange, "HTMLME durationchange event is expected only after changing MediaSource duration");
	assert_equals(e.target.custom_test_wrapper_update, "testing", "HTMLME wrapper, as adjusted by the test, should be retained");
	test.done();
	});
	});

	var setup_done_cb = test.step_func(function() {
	// Update the HTMLME JS wrapper with a custom property to be verified later.
	test_scope.video.custom_test_wrapper_update = "testing";
	test_scope.video = null;
	// \|test_scope.media_source\| should be the only remaining reference to HTMLME+MSE.
	// GC shouldn't collect HTMLME+MSE due to that live reference.
	assert_equals(test_scope.media_source.readyState, "open", "MediaSource object is open before gc().");
	gc();
	assert_equals(test_scope.media_source.readyState, "open", "MediaSource object is open after gc().");

	// Verify that HTMLME is still alive by changing the MediaSource object's duration, which causes
	// a durationchange event to become queued for dispatch on the attached HTMLME (and such dispatch ends this
	// test.)
	// Debug note: commenting out the next line demonstrates with debug logging that HTMLME+MSE is collected,
	// followed eventually by a timeout.
	test_scope.media_source.duration = 100;

	test_scope.expect_durationchange = true;
	test_scope.media_source = null;
	gc();
	});

	setup_htmlme_mse_lifetime_test(test, test_scope, handler_setup_cb, setup_done_cb)
	}, "GC of HTMLME+MediaSource preserves at least HTMLME and its wrapper when no references held by JS, but there is a pending HTMLME event");

	async_test(function(test) {
	var test_scope = new TestScope();

	var handler_setup_cb = null;

	var setup_done_cb = test.step_func(function() {
	assert_equals(test_scope.media_source.readyState, "open", "MediaSource object is open before gc().");
	test_scope.media_source = null;
	assert_equals(test_scope.video.src, test_scope.object_url, "HTMLME src attribute is correct before gc().");
	// \|test_scope.video\| should be the only remaining reference to HTMLME+MSE.
	// GC shouldn't collect HTMLME+MSE due to that live reference.

	// Debug note: setting test_scope.video to null here, and commenting out the assert_equals()
	// and test.done() lines, below, demonstrates with debug logging that HTMLME+MSE is collected, followed
	// eventually by a timeout.
	gc();

	assert_equals(test_scope.video.src, test_scope.object_url, "HTMLME src attribute is correct after gc().");
	test.done();
	});

	setup_htmlme_mse_lifetime_test(test, test_scope, handler_setup_cb, setup_done_cb)
	}, "GC of HTMLME+MediaSource preserves at least HTMLME when only the HTMLME reference is held by JS");

	async_test(function(test) {
	// This test builds on the previous test. It should fail if the previous test fails.

	var test_scope = new TestScope();

	var handler_setup_cb = test.step_func(function() {
	test_scope.media_source.onsourceclose = test.step_func(function() {
	assert_true(test_scope.expect_sourceclose, "MediaSource sourceclose event is expected only after clearing HTMLME src attribute");
	// Both HTMLME.onerror and MediaSource.onsourceclose are required to finish this test.
	if (test_scope.received_error)
	test.done();
	test_scope.received_sourceclose = true;
	test_scope.expect_sourceclose = false; // Only one sourceclose is expected.
	});

	test_scope.video.onerror = test.step_func(function() {
	assert_true(test_scope.expect_error, "HTMLME error event is expected only after clearing HTMLME src attribute");
	// Both HTMLME.onerror and MediaSource.onsourceclose are required to finish this test.
	if (test_scope.received_sourceclose)
	test.done();
	test_scope.received_error = true;
	test_scope.expect_error = false; // Only one error is expected.
	});
	});

	var setup_done_cb = test.step_func(function() {
	assert_equals(test_scope.media_source.readyState, "open", "MediaSource object is open before gc().");
	test_scope.media_source = null;
	assert_equals(test_scope.video.src, test_scope.object_url, "HTMLME src attribute is correct before gc().");
	// \|test_scope.video\| should be the only remaining reference to HTMLME+MSE.
	// GC shouldn't collect HTMLME+MSE due to that live reference.

	gc();

	assert_equals(test_scope.video.src, test_scope.object_url, "HTMLME src attribute is correct after gc().");

	// Verify that MediaSource is still alive by clearing the HTMLME object's src attribute, which causes a
	// sourceclose event to become queued for dispatch on the previously attached MediaSource and an error
	// event to become queued for dispatch on the HTMLME object (and such dispatches end this test.)
	// Debug note: commenting out the next line should result in test timeout.
	test_scope.video.src = "";
	test_scope.expect_sourceclose = true;
	test_scope.expect_error = true;
	});

	setup_htmlme_mse_lifetime_test(test, test_scope, handler_setup_cb, setup_done_cb)
	}, "GC of HTMLME+MediaSource preserves at least MediaSource and HTMLME when only the HTMLME reference is held by JS");

	async_test(function(test) {
	// This test builds on the previous two tests. It should fail if either of the previous two tests fails.

	var test_scope = new TestScope();

	var handler_setup_cb = test.step_func(function() {
	test_scope.media_source.onsourceclose = test.step_func(function(e) {
	assert_true(test_scope.expect_sourceclose, "MediaSource sourceclose event is expected only after clearing HTMLME src attribute");
	assert_equals(e.target.custom_test_wrapper_update, "testing-mediasource", "MediaSource wrapper, as adjusted by the test, should be retained");
	// Both HTMLME.onerror and MediaSource.onsourceclose are required to finish this test.
	if (test_scope.received_error)
	test.done();
	test_scope.received_sourceclose = true;
	test_scope.expect_sourceclose = false; // Only one sourceclose is expected.
	});

	test_scope.video.onerror = test.step_func(function(e) {
	assert_true(test_scope.expect_error, "HTMLME error event is expected only after clearing HTMLME src attribute");
	assert_equals(e.target.custom_test_wrapper_update, "testing-htmlme", "HTMLME wrapper, as adjusted by the test, should be retained");
	// Both HTMLME.onerror and MediaSource.onsourceclose are required to finish this test.
	if (test_scope.received_sourceclose)
	test.done();
	test_scope.received_error = true;
	test_scope.expect_error = false; // Only one error is expected.
	});
	});

	var setup_done_cb = test.step_func(function() {
	// Update the HTMLME and MediaSource JS wrappers with custom properties to be verified later.
	test_scope.video.custom_test_wrapper_update = "testing-htmlme";
	test_scope.media_source.custom_test_wrapper_update = "testing-mediasource";

	assert_equals(test_scope.media_source.readyState, "open", "MediaSource object is open before gc().");
	test_scope.media_source = null;
	assert_equals(test_scope.video.src, test_scope.object_url, "HTMLME src attribute is correct before gc().");
	// \|test_scope.video\| should be the only remaining reference to HTMLME+MSE.
	// GC shouldn't collect HTMLME+MSE due to that live reference.

	gc();

	assert_equals(test_scope.video.src, test_scope.object_url, "HTMLME src attribute is correct after gc().");

	// Verify that MediaSource is still alive by clearing the HTMLME object's src attribute, which causes a
	// sourceclose event to become queued for dispatch on the previously attached MediaSource and an error
	// event to become queued for dispatch on the HTMLME object (and such dispatches end this test.)
	// Debug note: commenting out the next line demonstrates with debug logging that HTMLME+MSE is collected,
	// followed eventually by a timeout.
	test_scope.video.src = "";

	test_scope.expect_sourceclose = true;
	test_scope.expect_error = true;
	test_scope.video = null;
	gc();
	});

	setup_htmlme_mse_lifetime_test(test, test_scope, handler_setup_cb, setup_done_cb)
	}, "GC of HTMLME+MediaSource preserves at least MediaSource and HTMLME and their wrappers when no references held by JS, but there is a pending event on each of HTMLME and MediaSource");

	async_test(function(test) {
	var test_scope = new TestScope();

	var handler_setup_cb = null;

	var setup_done_cb = test.step_func(function() {
	var source_buffer = test_scope.media_source.addSourceBuffer('video/webm; codecs="vp8"');
	test_scope.source_buffer_list = test_scope.media_source.sourceBuffers;
	source_buffer.custom_test_wrapper_update = "testing-sourcebuffer";
	assert_true(source_buffer === test_scope.source_buffer_list[0]);

	assert_equals(test_scope.media_source.readyState, "open", "MediaSource object is open before gc().");
	assert_equals(test_scope.video.src, test_scope.object_url, "HTMLME src attribute is correct before gc().");

	source_buffer = null;
	test_scope.media_source = null;
	test_scope.video = null;


	// \|test_scope.source_buffer_list\| should be the only remaining reference to HTMLME+MSE+SBL+SB.
	// GC shouldn't collected this group due to that live reference.

	// Debug note: setting test_scope.source_buffer_list to null here, and commenting out the assert_equals()
	// and test.done() lines, below, demonstrates with debug logging that HTMLME+MSE is collected, followed
	// eventually by a timeout.
	gc();

	assert_equals(test_scope.source_buffer_list.length, 1, "SBL should survive gc().");
	assert_equals(test_scope.source_buffer_list[0].custom_test_wrapper_update, "testing-sourcebuffer", "SBL[0]'s wrapper should survive gc().");
	test.done();
	});

	setup_htmlme_mse_lifetime_test(test, test_scope, handler_setup_cb, setup_done_cb)
	}, "GC of HTMLME+MediaSource+SBL+SB preserves at least SBL+SB when only the SourceBufferList reference is held by JS");

	// TODO(wolenetz): Consider further refactoring to extract specific testing concerns from the following test:
	async_test(function(test) {
	var video = document.createElement("video");
	var media_source = new MediaSource();
	var object_url = URL.createObjectURL(media_source);
	var malformed_media_append_started = false;

	video.onerror = test.step_func(function() {
	assert_true(malformed_media_append_started, "error should occur after append of malformed media bytestream started");
	test.done();
	});

	media_source.onsourceopen = test.step_func(function() {
	URL.revokeObjectURL(object_url);
	var source_buffer = media_source.addSourceBuffer('video/webm; codecs="vp8"');
	var source_buffer_list = media_source.sourceBuffers;
	assert_true(source_buffer === source_buffer_list[0]);
	source_buffer = null;
	media_source = null;
	video = null;
	// source_buffer_list's reference by us is the only thing keeping HTMLME+MSE alive.
	gc();

	setTimeout(test.step_func(function() {
	gc();
	source_buffer_list[0].onupdatestart = test.step_func(function() { malformed_media_append_started = true; });

	// Begin asynchronous append of a malformed media bytestream which
	// should result eventually with HTMLME error event firing due to the MSE
	// Append Error Algorithm.
	source_buffer_list[0].appendBuffer(new Uint8Array(10));

	// There should be a pending updatestart event on the SourceBuffer, so even if we drop the reference
	// to the SourceBufferList here, gc() still shouldn't collect HTMLME+MSE due to pending event dispatch
	// on MSE. This is verified by HTMLME eventually handling an error event due to the asynchronous append
	// of malformed media.
	source_buffer_list = null;
	gc();
	}), 0);
	});

	video.src = object_url;

	// Debugging notes: If this test times out, it's likely due to failure in
	// keeping HTMLME+MSE alive and pending event dispatch on their wrappers alive
	// through gc(); either gc() over-collected HTMLME+MSE or event dispatch was
	// perturbed by gc().
	// If the assert in video.onerror fails, it is self-explanatory.
	}, "GC of HTMLME+MediaSource+SBL+SB preserves all when only SourceBufferList reference is alive, then SourceBuffer.onupdatestart and HTMLME.onerror are dispatched if they became pending during the asynchronous buffer append algorithm, of malformed bytestream, after all HTMLME+MSE references dropped");

	</script>