Bug 1289993. Part 1 - Disconnect seek requests when shutting down MediaDecoder. r=kaku

MozReview-Commit-ID: 6av1OiJatCr

--HG--
extra : rebase_source : 66891c09e3c35029e7d8f1e605b026968019e353

dom/media/MediaDecoder.cpp

@@ -619,6 +619,8 @@ MediaDecoder::Shutdown()
   mCDMProxyPromiseHolder.RejectIfExists(true, __func__);
 #endif
 
+  DiscardOngoingSeekIfExists();
+
   // This changes the decoder state to SHUTDOWN and does other things
   // necessary to unblock the state machine thread if it's blocked, so
   // the asynchronous shutdown in nsDestroyStateMachine won't deadlock.