Oilpan: Prepare to move EventQueue and its subclasses to Oilpan heap.

Source/core/html/HTMLMediaElement.cpp

Index: Source/core/html/HTMLMediaElement.cpp
diff --git a/Source/core/html/HTMLMediaElement.cpp b/Source/core/html/HTMLMediaElement.cpp
index af3e44e4494d0448e89dc1b8aefb4295c0965312..f8a7bc6f15f0886d6b044e344b0972e863558a18 100644
--- a/Source/core/html/HTMLMediaElement.cpp
+++ b/Source/core/html/HTMLMediaElement.cpp
@@ -303,8 +303,6 @@ HTMLMediaElement::~HTMLMediaElement()
 {
     WTF_LOG(Media, "HTMLMediaElement::~HTMLMediaElement");
 
-    m_asyncEventQueue->close();
-
 #if ENABLE(OILPAN)
     // If the HTMLMediaElement dies with the document we are not
     // allowed to touch the document to adjust delay load event counts
@@ -319,10 +317,13 @@ HTMLMediaElement::~HTMLMediaElement()
     if (ActiveDOMObject::executionContext())
         setShouldDelayLoadEvent(false);
 #else
+    // HTMLMediaElement and m_asyncEventQueue always become unreachable
+    // together. So HTMLMediaElemenet and m_asyncEventQueue are destructed in
+    // the same GC. We don't need to close it explicitly in Oilpan.
+    m_asyncEventQueue->close();
+
     setShouldDelayLoadEvent(false);
-#endif
 
-#if !ENABLE(OILPAN)
     if (m_textTracks)
         m_textTracks->clearOwner();
 
@@ -3651,6 +3652,7 @@ void HTMLMediaElement::defaultEventHandler(Event* event)
 
 void HTMLMediaElement::trace(Visitor* visitor)
 {
+    visitor->trace(m_asyncEventQueue);
     visitor->trace(m_error);
     visitor->trace(m_currentSourceNode);
     visitor->trace(m_nextChildNodeToConsider);