Bug 1369548 - HTMLMediaElement::SetMediaKeys should continue working even the decoder is shutting down. r=cpearce

The MediaKeys status inside a HTMLME cannot be reflected correctly if the mSetCDMRequest is disconnected in HTMLME::ShutdownDecoder.
This may happen when a page calls load() or sets new src right after setting MediaKeys to null.

MozReview-Commit-ID: 3BZOmw7BNFO

dom/html/HTMLMediaElement.cpp

@@ -1723,7 +1723,7 @@ void HTMLMediaElement::ShutdownDecoder()
 {
   RemoveMediaElementFromURITable();
   NS_ASSERTION(mDecoder, "Must have decoder to shut down");
-  mSetCDMRequest.DisconnectIfExists();
+
   mWaitingForKeyListener.DisconnectIfExists();
   if (mMediaSource) {
     mMediaSource->CompletePendingTransactions();
@@ -4064,6 +4064,8 @@ HTMLMediaElement::~HTMLMediaElement()
     mVideoFrameContainer->ForgetElement();
   }
   UnregisterActivityObserver();
+
+  mSetCDMRequest.DisconnectIfExists();
   if (mDecoder) {
     ShutdownDecoder();
   }