Backed out 2 changesets (bug 1511235) for causing bugs 1513454, 1513456 as alwu requested on irc. a=backout

Backed out changeset 4c9f874d6868 (bug 1511235)
Backed out changeset 3432e8bee7f1 (bug 1511235)

dom/html/HTMLMediaElement.cpp

@@ -1630,10 +1630,6 @@ void HTMLMediaElement::SetVisible(bool aVisible) {
   }
 }
 
-bool HTMLMediaElement::IsVideoDecodingSuspended() const {
-  return mDecoder && mDecoder->IsVideoDecodingSuspended();
-}
-
 already_AddRefed<layers::Image> HTMLMediaElement::GetCurrentImage() {
   MarkAsTainted();