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 * modification, are permitted provided that the following conditions are
 * met:
 *
 *     * Redistributions of source code must retain the above copyright
 * notice, this list of conditions and the following disclaimer.
 *     * Redistributions in binary form must reproduce the above
 * copyright notice, this list of conditions and the following disclaimer
 * in the documentation and/or other materials provided with the
 * distribution.
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 * contributors may be used to endorse or promote products derived from
 * this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
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 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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#include "third_party/blink/renderer/bindings/core/v8/v8_gc_for_context_dispose.h"

#include "base/process/process_metrics.h"
#include "build/build_config.h"
#include "third_party/blink/public/platform/platform.h"
#include "third_party/blink/renderer/platform/bindings/v8_per_isolate_data.h"
#include "third_party/blink/renderer/platform/instrumentation/histogram.h"
#include "third_party/blink/renderer/platform/instrumentation/memory_pressure_listener.h"
#include "third_party/blink/renderer/platform/scheduler/public/thread_scheduler.h"
#include "third_party/blink/renderer/platform/wtf/std_lib_extras.h"
#include "v8/include/v8.h"

#if defined(OS_ANDROID)
static size_t GetMemoryUsage() {
  size_t usage =
      base::ProcessMetrics::CreateCurrentProcessMetrics()->GetMallocUsage() +
      WTF::Partitions::TotalActiveBytes() +
      blink::ProcessHeap::TotalAllocatedObjectSize();
  v8::HeapStatistics v8_heap_statistics;
  blink::V8PerIsolateData::MainThreadIsolate()->GetHeapStatistics(
      &v8_heap_statistics);
  usage += v8_heap_statistics.total_heap_size();
  return usage;
}
#endif  // defined(OS_ANDROID)

namespace blink {

V8GCForContextDispose::V8GCForContextDispose()
    : pseudo_idle_timer_(ThreadScheduler::Current()->V8TaskRunner(),
                         this,
                         &V8GCForContextDispose::PseudoIdleTimerFired),
      force_page_navigation_gc_(false) {
  Reset();
}

void V8GCForContextDispose::NotifyContextDisposed(
    bool is_main_frame,
    WindowProxy::FrameReuseStatus frame_reuse_status) {
  did_dispose_context_for_main_frame_ = is_main_frame;
  last_context_disposal_time_ = base::Time::Now();
#if defined(OS_ANDROID)
  // When a low end device is in a low memory situation we should prioritize
  // memory use and trigger a V8+Blink GC. However, on Android, if the frame
  // will not be reused, the process will likely to be killed soon so skip this.
  if (is_main_frame && frame_reuse_status == WindowProxy::kFrameWillBeReused &&
      ((MemoryPressureListenerRegistry::IsLowEndDevice() &&
        MemoryPressureListenerRegistry::IsCurrentlyLowMemory()) ||
       force_page_navigation_gc_)) {
    size_t pre_gc_memory_usage = GetMemoryUsage();
    V8PerIsolateData::MainThreadIsolate()->MemoryPressureNotification(
        v8::MemoryPressureLevel::kCritical);
    size_t post_gc_memory_usage = GetMemoryUsage();
    int reduction = static_cast<int>(pre_gc_memory_usage) -
                    static_cast<int>(post_gc_memory_usage);
    DEFINE_STATIC_LOCAL(
        CustomCountHistogram, reduction_histogram,
        ("BlinkGC.LowMemoryPageNavigationGC.Reduction", 1, 512, 50));
    reduction_histogram.Count(reduction / 1024 / 1024);

    force_page_navigation_gc_ = false;
  }
#endif
  V8PerIsolateData::MainThreadIsolate()->ContextDisposedNotification(
      !is_main_frame);
  pseudo_idle_timer_.Stop();
}

void V8GCForContextDispose::NotifyIdle() {
  constexpr base::TimeDelta kMaxTimeSinceLastContextDisposal =
      base::TimeDelta::FromMilliseconds(200);
  if (!did_dispose_context_for_main_frame_ && !pseudo_idle_timer_.IsActive() &&
      last_context_disposal_time_ + kMaxTimeSinceLastContextDisposal >=
          base::Time::Now()) {
    pseudo_idle_timer_.StartOneShot(base::TimeDelta(), FROM_HERE);
  }
}

V8GCForContextDispose& V8GCForContextDispose::Instance() {
  DEFINE_STATIC_LOCAL(V8GCForContextDispose, static_instance, ());
  return static_instance;
}

void V8GCForContextDispose::PseudoIdleTimerFired(TimerBase*) {
  V8PerIsolateData::MainThreadIsolate()->IdleNotificationDeadline(
      base::TimeTicks::Now().since_origin().InSecondsF());
  Reset();
}

void V8GCForContextDispose::Reset() {
  did_dispose_context_for_main_frame_ = false;
  last_context_disposal_time_ = base::Time();
}

void V8GCForContextDispose::SetForcePageNavigationGC() {
  force_page_navigation_gc_ = true;
}

}  // namespace blink