Bug 1308147. Part 5 - reject mPendingSeek in DormantState::Exit(). r=kikuo

MozReview-Commit-ID: HfQCWBNtUwZ

--HG--
extra : rebase_source : ebae0bc2c8c91a859eb254f5fa1c947abc869ed3
extra : source : 69296a28551d1e2d1013790e2cfd7e063beea246

dom/media/MediaDecoderStateMachine.cpp

@@ -444,8 +444,9 @@ public:
 
   void Exit() override
   {
-    // Transfer the seek job so it is available to the next state.
-    mMaster->mQueuedSeek = Move(mPendingSeek);
+    // mPendingSeek is either moved in HandleDormant() or should be rejected
+    // here before transition to SHUTDOWN.
+    mPendingSeek.RejectIfExists(__func__);
   }
 
   State GetState() const override