Move LayoutObject::m_previousPosition... into a global map in ObjectPaintInvalidator

third_party/WebKit/Source/core/paint/PaintInvalidator.h

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef PaintInvalidator_h
 #define PaintInvalidator_h
 
 #include "platform/geometry/LayoutRect.h"
 #include "platform/graphics/paint/GeometryMapper.h"
 #include "wtf/Vector.h"
@@ skipping 50 matching lines @@
   // The current paint invalidation container for stacked contents (stacking
   // contexts or positioned objects).  It is the nearest ancestor composited
   // object which establishes a stacking context.  See
   // Source/core/paint/README.md ### PaintInvalidationState for details on how
   // stacked contents' paint invalidation containers differ.
   const LayoutBoxModelObject* paintInvalidationContainerForStackedContents =
       nullptr;
 
   PaintLayer* paintingLayer = nullptr;
 
+  // Store the new and old visual rects in the paint invalidation backing's
+  // coordinates. The rects do *not* account for composited scrolling.
+  // See LayoutObject::adjustVisualRectForCompositedScrolling().
   LayoutRect oldVisualRect;
   LayoutRect newVisualRect;
+
+  // Store the origin of the object's local coordinates in the paint
+  // invalidation backing's coordinates. They are used to detect layoutObject
+  // shifts that forces a full invalidation.

[chrishtr, 2016/11/04 18:20:07]

nit: s/forces/force/

[Xianzhu, 2016/11/04 19:11:03]

Done.

+  // The points do *not* account for composited scrolling. See
+  // LayoutObject::adjustVisualRectForCompositedScrolling().
   LayoutPoint oldLocation;
   LayoutPoint newLocation;
 };
 
 class PaintInvalidator {
  public:
   void invalidatePaintIfNeeded(FrameView&, PaintInvalidatorContext&);
   void invalidatePaintIfNeeded(const LayoutObject&, PaintInvalidatorContext&);
 
   // Process objects needing paint invalidation on the next frame.
   // See the definition of PaintInvalidationDelayedFull for more details.
   void processPendingDelayedPaintInvalidations();
 
  private:
   LayoutRect mapLocalRectToPaintInvalidationBacking(
       const LayoutObject&,
       const FloatRect&,
       const PaintInvalidatorContext&);
   LayoutRect computeVisualRectInBacking(const LayoutObject&,
                                         const PaintInvalidatorContext&);
-  LayoutPoint computeLocationFromPaintInvalidationBacking(
-      const LayoutObject&,
-      const PaintInvalidatorContext&);
+  LayoutPoint computeLocationInBacking(const LayoutObject&,
+                                       const PaintInvalidatorContext&);
   void updatePaintingLayer(const LayoutObject&, PaintInvalidatorContext&);
   void updateContext(const LayoutObject&, PaintInvalidatorContext&);
 
   Vector<const LayoutObject*> m_pendingDelayedPaintInvalidations;
   GeometryMapper m_geometryMapper;
 };
 
 }  // namespace blink
 
 #endif  // PaintInvalidator_h