Bug 1305969 - Ensure we don't clear the paint sync id unless it has actually been sent to Java via SyncViewportInfo. r=rbarker

MozReview-Commit-ID: FXy6xeWjqHq

--HG--
extra : rebase_source : 8887d1c7b99c8449c545023047b2ccc392977366

gfx/layers/composite/AsyncCompositionManager.cpp

@@ -1007,9 +1007,9 @@ AsyncCompositionManager::ApplyAsyncContentTransformToTree(Layer *aLayer,
                     mPaintSyncId, fixedLayerMargins);
                 mFixedLayerMargins = fixedLayerMargins;
                 mLayersUpdated = false;
+                mPaintSyncId = 0;
               }
               mIsFirstPaint = false;
-              mPaintSyncId = 0;
             }
           }
 #else