Bug 1287021: [MSE] Set delaying-the-load-event-flag to false when attaching media source. r=jwwang

MozReview-Commit-ID: IsF1BPHrjce

--HG--
extra : rebase_source : 5639c3007979c2cdc2f5ac284cee068a1382aa14

dom/html/HTMLMediaElement.cpp

@@ -1538,6 +1538,7 @@ nsresult HTMLMediaElement::LoadResource()
       decoder->Shutdown();
       return NS_ERROR_FAILURE;
     }
+    ChangeDelayLoadStatus(false);
     RefPtr<MediaResource> resource =
       MediaSourceDecoder::CreateResource(mMediaSource->GetPrincipal());
     return FinishDecoderSetup(decoder, resource, nullptr);