Bug 1334112 -part3 : Trigger UpdateReadyState after unbind TrackElement's and TextTrack::SetReadyState. r=rillian

MozReview-Commit-ID: pEeOzZSpak

dom/html/HTMLTrackElement.cpp

@@ -392,6 +392,7 @@ HTMLTrackElement::UnbindFromTree(bool aDeep, bool aNullParent)
     // called.
     if (mTrack) {
       mMediaParent->RemoveTextTrack(mTrack);
+      mMediaParent->UpdateReadyState();
     }
     mMediaParent = nullptr;
   }