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

Source/platform/heap/HeapTest.cpp

Index: Source/platform/heap/HeapTest.cpp
diff --git a/Source/platform/heap/HeapTest.cpp b/Source/platform/heap/HeapTest.cpp
index 3cfbc5357d5efa316d8e47d287330a358c4c8172..5d0f2b2136eb08a45d9741f705b82a89bb54ed3c 100644
--- a/Source/platform/heap/HeapTest.cpp
+++ b/Source/platform/heap/HeapTest.cpp
@@ -5571,4 +5571,18 @@ TEST(HeapTest, StackGrowthDirection)
     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