diff -aruN nspr-4.8.6/mozilla/nsprpub/pr/include/prlock.h nspr-4.8.6.N/mozilla/nsprpub/pr/include/prlock.h
--- nspr-4.8.6/mozilla/nsprpub/pr/include/prlock.h	2009-03-18 14:29:29.000000000 -0700
+++ nspr-4.8.6.N/mozilla/nsprpub/pr/include/prlock.h	2016-08-26 08:21:19.494206783 -0700
@@ -117,6 +117,18 @@
 NSPR_API(PRStatus) PR_Unlock(PRLock *lock);
 
 /***********************************************************************
+** FUNCTION:    PR_IsLocked
+** DESCRIPTION:
+**  Determine if a lock is locked.
+** INPUTS:      PRLock *lock
+**              Lock to determine.
+** OUTPUTS:     void
+** RETURN:      PRBool
+**              Returns PR_TRUE if lock is locked, else PR_FALSE.
+***********************************************************************/
+NSPR_API(PRBool) PR_IsLocked(PRLock *lock);
+
+/***********************************************************************
 ** MACRO:    PR_ASSERT_CURRENT_THREAD_OWNS_LOCK
 ** DESCRIPTION:
 **  If the current thread owns |lock|, this assertion is guaranteed to
diff -aruN nspr-4.8.6/mozilla/nsprpub/pr/src/pthreads/ptsynch.c nspr-4.8.6.N/mozilla/nsprpub/pr/src/pthreads/ptsynch.c
--- nspr-4.8.6/mozilla/nsprpub/pr/src/pthreads/ptsynch.c	2010-07-11 10:14:39.000000000 -0700
+++ nspr-4.8.6.N/mozilla/nsprpub/pr/src/pthreads/ptsynch.c	2016-08-26 08:12:02.026296557 -0700
@@ -245,6 +245,12 @@
     return PR_SUCCESS;
 }  /* PR_Unlock */
 
+PR_IMPLEMENT(PRBool) PR_IsLocked(PRLock *lock)
+{
+    PR_ASSERT(lock != NULL);
+    return lock->locked;
+}
+
 PR_IMPLEMENT(void) PR_AssertCurrentThreadOwnsLock(PRLock *lock)
 {
     /* Nb: the order of the |locked| and |owner==me| checks is not critical