Bug 1445019 - Use the compositing transform when checking for unused APZ transforms. r=botond

MozReview-Commit-ID: 1o1RANM3yxo

--HG--
extra : rebase_source : 1d05cda7c7677df58f8ce8f1a46d51498d52c734

gfx/layers/apz/src/APZSampler.cpp

@@ -207,7 +207,7 @@ APZSampler::HasUnusedAsyncTransform(const LayerMetricsWrapper& aLayer)
   AsyncPanZoomController* apzc = aLayer.GetApzc();
   return apzc
       && !apzc->GetAsyncTransformAppliedToContent()
-      && !AsyncTransformComponentMatrix(apzc->GetCurrentAsyncTransform(AsyncPanZoomController::eForHitTesting)).IsIdentity();
+      && !AsyncTransformComponentMatrix(apzc->GetCurrentAsyncTransform(AsyncPanZoomController::eForCompositing)).IsIdentity();
 }
 
 } // namespace layers