Bug 1414762 - imgRequestProxy::CancelAndForgetObserver should always force load group removal to dispatch. r=tnikkel

imgRequestProxy::CancelAndForgetObserver was intended to always dispatch
any load group removals due to reentracy conflicts with the callers.
However in bug 1404422 the fact that imgRequest::RemoveProxy can
indirectly trigger a load group removal through completing an
incompleted request.

image/imgRequestProxy.cpp

@@ -515,12 +515,12 @@ imgRequestProxy::CancelAndForgetObserver(nsresult aStatus)
   LOG_SCOPE(gImgLog, "imgRequestProxy::CancelAndForgetObserver");
 
   mCanceled = true;
+  mForceDispatchLoadGroup = true;
 
   if (GetOwner()) {
     GetOwner()->RemoveProxy(this, aStatus);
   }
 
-  mForceDispatchLoadGroup = true;
   RemoveFromLoadGroup();
   mForceDispatchLoadGroup = false;