Fix the bug that negative outline-offset is covered up by composited

third_party/WebKit/Source/core/layout/compositing/CompositedLayerMapping.h

 /*
  * Copyright (C) 2009, 2010, 2011 Apple Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 102 matching lines @@
   bool hasAncestorClippingLayer() const {
     return m_ancestorClippingLayer.get();
   }
   GraphicsLayer* ancestorClippingLayer() const {
     return m_ancestorClippingLayer.get();
   }
 
   GraphicsLayer* foregroundLayer() const { return m_foregroundLayer.get(); }
 
   GraphicsLayer* backgroundLayer() const { return m_backgroundLayer.get(); }
+
+  GraphicsLayer* decorationLayer() const { return m_decorationLayer.get(); }
+
   bool backgroundLayerPaintsFixedRootBackground() const {
     return m_backgroundLayerPaintsFixedRootBackground;
   }
 
   bool hasScrollingLayer() const { return m_scrollingLayer.get(); }
   GraphicsLayer* scrollingLayer() const { return m_scrollingLayer.get(); }
   GraphicsLayer* scrollingContentsLayer() const {
     return m_scrollingContentsLayer.get();
   }
 
@@ skipping 213 matching lines @@
   void updateChildTransformLayerGeometry();
   void updateMaskLayerGeometry();
   void updateTransformGeometry(
       const IntPoint& snappedOffsetFromCompositedAncestor,
       const IntRect& relativeCompositingBounds);
   void updateForegroundLayerGeometry(
       const FloatSize& relativeCompositingBoundsSize,
       const IntRect& clippingBox);
   void updateBackgroundLayerGeometry(
       const FloatSize& relativeCompositingBoundsSize);
+  void updateDecorationLayerGeometry(
+      const FloatSize& relativeCompositingBoundsSize);
   void updateScrollingLayerGeometry(const IntRect& localCompositingBounds);
   void updateChildClippingMaskLayerGeometry();
 
   void createPrimaryGraphicsLayer();
   void destroyGraphicsLayers();
 
   std::unique_ptr<GraphicsLayer> createGraphicsLayer(
       CompositingReasons,
       SquashingDisallowedReasons = SquashingDisallowedReasonsNone);
   bool toggleScrollbarLayerIfNeeded(std::unique_ptr<GraphicsLayer>&,
@@ skipping 10 matching lines @@
   void updateInternalHierarchy();
   void updatePaintingPhases();
   bool updateClippingLayers(bool needsAncestorClip, bool needsDescendantClip);
   bool updateChildTransformLayer(bool needsChildTransformLayer);
   bool updateOverflowControlsLayers(bool needsHorizontalScrollbarLayer,
                                     bool needsVerticalScrollbarLayer,
                                     bool needsScrollCornerLayer,
                                     bool needsAncestorClip);
   bool updateForegroundLayer(bool needsForegroundLayer);
   bool updateBackgroundLayer(bool needsBackgroundLayer);
+  bool updateDecorationLayer(bool needsDecorationLayer);
   bool updateMaskLayer(bool needsMaskLayer);
   void updateChildClippingMaskLayer(bool needsChildClippingMaskLayer);
   bool requiresHorizontalScrollbarLayer() const {
     return m_owningLayer.getScrollableArea() &&
            m_owningLayer.getScrollableArea()->horizontalScrollbar();
   }
   bool requiresVerticalScrollbarLayer() const {
     return m_owningLayer.getScrollableArea() &&
            m_owningLayer.getScrollableArea()->verticalScrollbar();
   }
@@ skipping 89 matching lines @@
   // The hierarchy of layers that is maintained by the CompositedLayerMapping
   // looks like this:
   //
   //  + m_ancestorClippingLayer [OPTIONAL]
   //    + m_graphicsLayer
   //      + m_childTransformLayer [OPTIONAL]
   //      | + m_childContainmentLayer [OPTIONAL]
   //      |   <-OR->
   //      |   (m_scrollingLayer + m_scrollingContentsLayer) [OPTIONAL]
   //      + m_overflowControlsAncestorClippingLayer [OPTIONAL]
-  //        + m_overflowControlsHostLayer [OPTIONAL]
-  //          + m_layerForVerticalScrollbar [OPTIONAL]
-  //          + m_layerForHorizontalScrollbar [OPTIONAL]
-  //          + m_layerForScrollCorner [OPTIONAL]
+  //      | + m_overflowControlsHostLayer [OPTIONAL]
+  //      |   + m_layerForVerticalScrollbar [OPTIONAL]
+  //      |   + m_layerForHorizontalScrollbar [OPTIONAL]
+  //      |   + m_layerForScrollCorner [OPTIONAL]
+  //      + m_decorationLayer [OPTIONAL]
   // The overflow controls may need to be repositioned in the graphics layer
   // tree by the RLC to ensure that they stack above scrolling content.
   //
   // We need an ancestor clipping layer if our clipping ancestor is not our
   // ancestor in the clipping tree. Here's what that might look like.
   //
   // Let A = the clipping ancestor,
   //     B = the clip descendant, and
   //     SC = the stacking context that is the ancestor of A and B in the
   //          stacking tree.
@@ skipping 84 matching lines @@
 
   // The reparented overflow controls sometimes need to be clipped by a
   // non-ancestor. In just the same way we need an ancestor clipping layer to
   // clip this CLM's internal hierarchy, we add another layer to clip the
   // overflow controls. We could combine this with m_overflowControlsHostLayer,
   // but that would require manually intersecting their clips, and shifting the
   // overflow controls to compensate for this clip's offset. By using a separate
   // layer, the overflow controls can remain ignorant of ancestor clipping.
   std::unique_ptr<GraphicsLayer> m_overflowControlsAncestorClippingLayer;
 
+  // DecorationLayer which includes painting of outline etc.

[chrishtr, 2016/11/17 22:40:21]

etc? What does it paint except outline?

+  std::unique_ptr<GraphicsLayer> m_decorationLayer;
+
   // A squashing CLM has two possible squashing-related structures.
   //
   // If m_ancestorClippingLayer is present:
   //
   // m_ancestorClippingLayer
   //   + m_graphicsLayer
   //   + m_squashingLayer
   //
   // If not:
   //
@@ skipping 37 matching lines @@
   // Keep track of whether the background is painted onto the scrolling contents
   // layer for invalidations.
   unsigned m_backgroundPaintsOntoScrollingContentsLayer : 1;
 
   friend class CompositedLayerMappingTest;
 };
 
 }  // namespace blink
 
 #endif  // CompositedLayerMapping_h