Bug 959847. Part 8. Don't let ProcessDisplayItems set the clip on subdocument items when they are being used to draw the display port content. r=roc

layout/base/FrameLayerBuilder.cpp

@@ -2452,8 +2452,6 @@ ContainerState::ProcessDisplayItems(const nsDisplayList& aList,
         continue;
       }
 
-      bool setVisibleRegion = (itemType != nsDisplayItem::TYPE_TRANSFORM) &&
-        (itemType != nsDisplayItem::TYPE_SCROLL_LAYER);
       if (itemType == nsDisplayItem::TYPE_TRANSFORM) {
         mParameters.mAncestorClipRect = itemClip.HasClip() ? &clipRect : nullptr;
       } else {
@@ -2526,7 +2524,7 @@ ContainerState::ProcessDisplayItems(const nsDisplayList& aList,
         }
       }
       itemVisibleRect.MoveBy(mParameters.mOffset);
-      if (setVisibleRegion) {
+      if (item->SetVisibleRegionOnLayer()) {
         SetVisibleRegionForLayer(ownLayer, ownLayer->GetVisibleRegion(), itemVisibleRect);
       }
 

layout/base/nsDisplayList.h

@@ -1233,6 +1233,11 @@ public:
     mClip = aBuilder->AllocateDisplayItemClip(aClip);
   }
 
+  // If we return false here it means that if this item creates a layer then
+  // ProcessDisplayItems will not set the visible region on the layer. The item
+  // should set the visible region, usually in BuildContainerLayer.
+  virtual bool SetVisibleRegionOnLayer() { return true; }
+
 protected:
   friend class nsDisplayList;
 
@@ -2715,6 +2720,9 @@ public:
   virtual already_AddRefed<Layer> BuildLayer(nsDisplayListBuilder* aBuilder,
                                              LayerManager* aManager,
                                              const ContainerLayerParameters& aContainerParameters) MOZ_OVERRIDE;
+
+  virtual bool SetVisibleRegionOnLayer() MOZ_OVERRIDE { return !(mFlags & GENERATE_SCROLLABLE_LAYER); }
+
   NS_DISPLAY_DECL_NAME("SubDocument", TYPE_SUBDOCUMENT)
 };
 
@@ -2844,6 +2852,8 @@ public:
   virtual nsIFrame* GetScrollFrame() { return mScrollFrame; }
   virtual nsIFrame* GetScrolledFrame() { return mScrolledFrame; }
 
+  virtual bool SetVisibleRegionOnLayer() MOZ_OVERRIDE { return false; }
+
 #ifdef MOZ_DUMP_PAINTING
   virtual void WriteDebugInfo(nsACString& aTo) MOZ_OVERRIDE;
 #endif
@@ -3202,6 +3212,8 @@ public:
                                                 bool aLogAnimations = false);
   bool CanUseAsyncAnimations(nsDisplayListBuilder* aBuilder) MOZ_OVERRIDE;
 
+  virtual bool SetVisibleRegionOnLayer() MOZ_OVERRIDE { return false; }
+
 private:
   static gfx3DMatrix GetResultingTransformMatrixInternal(const FrameTransformProperties& aProperties,
                                                          const nsPoint& aOrigin,