Bug 1547757 - Use a RefPtr to hold owner element ref when moving media resource load to background. r=cpearce

Differential Revision: https://phabricator.services.mozilla.com/D31019

--HG--
extra : moz-landing-system : lando

dom/media/BaseMediaResource.cpp

@@ -114,7 +114,7 @@ void BaseMediaResource::SetLoadInBackground(bool aLoadInBackground) {
     NS_WARNING("Null owner in MediaResource::SetLoadInBackground()");
     return;
   }
-  dom::HTMLMediaElement* element = owner->GetMediaElement();
+  RefPtr<dom::HTMLMediaElement> element = owner->GetMediaElement();
   if (!element) {
     NS_WARNING("Null element in MediaResource::SetLoadInBackground()");
     return;