Oilpan: Make MediaControllers ExecutionContext a weak pointer.

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 13c824a8b3de7745340fbeacc4afa320259a8ab7..8388b864111e9f53da11de3acf520e97bd40cfb7 100644
--- a/Source/core/html/HTMLMediaElement.cpp
+++ b/Source/core/html/HTMLMediaElement.cpp
@@ -3190,8 +3190,12 @@ bool HTMLMediaElement::hasPendingActivity() const
 
 void HTMLMediaElement::contextDestroyed()
 {
+    // With Oilpan the ExecutionContext is weakly referenced from the media
+    // controller and so it will clear itself on destruction.
+#if !ENABLE(OILPAN)
     if (m_mediaController)
         m_mediaController->clearExecutionContext();
+#endif
     ActiveDOMObject::contextDestroyed();
 }