#457: M1419363 + WeakPtr support from M1267918

dom/html/HTMLMediaElement.cpp

@@ -3110,11 +3110,13 @@ public:
   {
     NS_ASSERTION(NS_IsMainThread(), "Should be on main thread.");
 
+    if (MOZ_UNLIKELY(!mElement)) return; // bug 1419363
+
     mElement->NotifyMediaStreamTracksAvailable(aStream);
   }
 
 private:
-  HTMLMediaElement* mElement;
+  WeakPtr<HTMLMediaElement> mElement;
 };
 
 class HTMLMediaElement::MediaStreamTrackListener :

dom/html/HTMLMediaElement.h

@@ -18,6 +18,7 @@
 #include "mozilla/Attributes.h"
 #include "mozilla/dom/Promise.h"
 #include "mozilla/dom/TextTrackManager.h"
+#include "mozilla/WeakPtr.h"
 #include "MediaDecoder.h"
 #ifdef MOZ_EME
 #include "mozilla/dom/MediaKeys.h"
@@ -76,7 +77,8 @@ class HTMLMediaElement : public nsGenericHTMLElement,
                          public nsIDOMHTMLMediaElement,
                          public nsIObserver,
                          public MediaDecoderOwner,
-                         public nsIAudioChannelAgentCallback
+                         public nsIAudioChannelAgentCallback,
+                         public SupportsWeakPtr<HTMLMediaElement>
 {
   friend AutoNotifyAudioChannelAgent;
 
@@ -89,6 +91,8 @@ public:
   typedef mozilla::MediaDecoderOwner MediaDecoderOwner;
   typedef mozilla::MetadataTags MetadataTags;
 
+  MOZ_DECLARE_WEAKREFERENCE_TYPENAME(HTMLMediaElement)
+
   CORSMode GetCORSMode() {
     return mCORSMode;
   }