WebAudio: Fix AudioNode leak in a case that AudioNode is not disconnected from the graph explicitly.

Source/platform/heap/HeapTest.cpp

 /*
  * Copyright (C) 2013 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * 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
@@ skipping 5553 matching lines @@
 } // namespace
 
 TEST(HeapTest, StackGrowthDirection)
 {
     // The implementation of marking probes stack usage as it runs,
     // and has a builtin assumption that the stack grows towards
     // lower addresses.
     EXPECT_EQ(GrowsTowardsLower, stackGrowthDirection());
 }
 
+TEST(HeapTest, Zombie)
+{
+    Bar::s_live = 0;
+    Baz* baz = Baz::create(Bar::create());
+    ThreadState::current()->markAsZombie(baz);
+    Heap::collectGarbage(ThreadState::NoHeapPointersOnStack);
+    // |baz| and a Bar shouldn't be collected.
+    EXPECT_EQ(1u, Bar::s_live);
+
+    ThreadState::current()->purifyZombies();
+    Heap::collectGarbage(ThreadState::NoHeapPointersOnStack);
+    EXPECT_EQ(0u, Bar::s_live);
+}
+
 } // namespace blink