Bug 1369910 - Simplify AddingOwnLayer() call sites in ProcessDisplayItems(). r=mstange

MozReview-Commit-ID: 3kH48WPAOv7

--HG--
extra : rebase_source : 8bb31b37762f26383de3a1353aa8b70be243130a

layout/painting/FrameLayerBuilder.cpp

@@ -4216,18 +4216,22 @@ ContainerState::ProcessDisplayItems(nsDisplayList* aList)
         mPaintedLayerDataTree.AddingOwnLayer(clipAGR,
                                              &scrolledClipRect,
                                              uniformColorPtr);
-      } else if ((*animatedGeometryRoot == item->Frame() &&
-                  *animatedGeometryRoot != mBuilder->RootReferenceFrame()) ||
-                 (IsScrollThumbLayer(item) && mManager->IsWidgetLayerManager())) {
-        // This is the case for scrollbar thumbs, for example. In that case the
-        // clip we care about is the overflow:hidden clip on the scrollbar.
+      } else if (IsScrollThumbLayer(item) && mManager->IsWidgetLayerManager()) {
+        // For scrollbar thumbs, the clip we care about is the clip added by the
+        // slider frame.
         mPaintedLayerDataTree.AddingOwnLayer(animatedGeometryRoot->mParentAGR,
                                              clipPtr,
                                              uniformColorPtr);
-      } else if (prerenderedTransform) {
-        mPaintedLayerDataTree.AddingOwnLayer(animatedGeometryRoot,
-                                             clipPtr,
-                                             uniformColorPtr);
+      } else if (prerenderedTransform && mManager->IsWidgetLayerManager()) {
+        if (animatedGeometryRoot->mParentAGR) {
+          mPaintedLayerDataTree.AddingOwnLayer(animatedGeometryRoot->mParentAGR,
+                                               clipPtr,
+                                               uniformColorPtr);
+        } else {
+          mPaintedLayerDataTree.AddingOwnLayer(animatedGeometryRoot,
+                                               nullptr,
+                                               uniformColorPtr);
+        }
       } else {
         // Using itemVisibleRect here isn't perfect. itemVisibleRect can be
         // larger or smaller than the potential bounds of item's contents in

layout/painting/nsDisplayList.cpp

@@ -6187,6 +6187,13 @@ nsDisplaySubDocument::nsDisplaySubDocument(nsDisplayListBuilder* aBuilder,
   mForceDispatchToContentRegion =
     aBuilder->IsBuildingLayerEventRegions() &&
     nsLayoutUtils::HasDocumentLevelListenersForApzAwareEvents(aFrame->PresContext()->PresShell());
+
+  // The SubDocument display item is conceptually outside the viewport frame,
+  // so in cases where the viewport frame is an AGR, the SubDocument's AGR
+  // should be not the viewport frame itself, but its parent AGR.
+  if (*mAnimatedGeometryRoot == mFrame && mAnimatedGeometryRoot->mParentAGR) {
+    mAnimatedGeometryRoot = mAnimatedGeometryRoot->mParentAGR;
+  }
 }
 
 #ifdef NS_BUILD_REFCNT_LOGGING