--- a/dom/media/MediaDecoderStateMachine.cpp
+++ b/dom/media/MediaDecoderStateMachine.cpp
@@ -876,17 +876,18 @@ nsresult MediaDecoderStateMachine::Init(
     OwnerThread(), __func__, this,
     &MediaDecoderStateMachine::OnCDMProxyReady,
     &MediaDecoderStateMachine::OnCDMProxyNotReady));
 #endif
 
   nsresult rv = mReader->Init();
   NS_ENSURE_SUCCESS(rv, rv);
 
-  OwnerThread()->Dispatch(NewRunnableMethod(this, &MediaDecoderStateMachine::ReadMetadata));
+  OwnerThread()->Dispatch(NewRunnableMethod<State>(
+    this, &MediaDecoderStateMachine::EnterState, mState.Ref()));
 
   return NS_OK;
 }
 
 void
 MediaDecoderStateMachine::SetMediaDecoderReaderWrapperCallback()
 {
   MOZ_ASSERT(OnTaskQueue());
@@ -1089,16 +1090,20 @@ MediaDecoderStateMachine::ExitState(Stat
   }
 }
 
 void
 MediaDecoderStateMachine::EnterState(State aState)
 {
   MOZ_ASSERT(OnTaskQueue());
   switch (aState) {
+    case DECODER_STATE_DECODING_METADATA:
+      mDecodingFirstFrame = true;
+      ReadMetadata();
+      break;
     case DECODER_STATE_ERROR:
     case DECODER_STATE_SHUTDOWN:
       mIsShutdown = true;
       break;
     default:
       break;
   }
 }
@@ -1216,18 +1221,16 @@ MediaDecoderStateMachine::SetDormant(boo
     // rely on it here as well.
     mReader->ReleaseResources();
 
     return;
   }
 
   // Exit dormant state.
   SetState(DECODER_STATE_DECODING_METADATA);
-  mDecodingFirstFrame = true;
-  ReadMetadata();
 }
 
 RefPtr<ShutdownPromise>
 MediaDecoderStateMachine::Shutdown()
 {
   MOZ_ASSERT(OnTaskQueue());
 
   // Once we've entered the shutdown state here there's no going back.