Bug 1143575. Async image invalidation does not necessarily need to invalidate the layer; LayerTreeInvalidation will do that for us. r=mattwoodrow

We need to remove this so that adding images to the end of the list of images
for an ImageLayer doesn't force composition to happen even if nothing else
has changed.

--HG--
extra : commitid : 8ycbGC3r3R2
extra : rebase_source : 2db81491d697d45e2e2c4605a3a00db7aca8586b

gfx/layers/ipc/CompositableTransactionParent.cpp

@@ -196,9 +196,6 @@ CompositableParentManager::ReceiveCompositableUpdate(const CompositableOperation
 
       if (IsAsync() && compositable->GetLayer()) {
         ScheduleComposition(op);
-        // Async layer updates don't trigger invalidation, manually tell the layer
-        // that its content have changed.
-        compositable->GetLayer()->SetInvalidRectToVisibleRegion();
       }
       break;
     }