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

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

Index: third_party/WebKit/Source/core/paint/PaintInvalidator.h
diff --git a/third_party/WebKit/Source/core/paint/PaintInvalidator.h b/third_party/WebKit/Source/core/paint/PaintInvalidator.h
index c03834d7c33d0b25ac06dd2c41d37302effbed56..567f430a9a09b4cbdf8497ab92961976683ca1d9 100644
--- a/third_party/WebKit/Source/core/paint/PaintInvalidator.h
+++ b/third_party/WebKit/Source/core/paint/PaintInvalidator.h
@@ -68,8 +68,17 @@ struct PaintInvalidatorContext {
 
   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 force a full invalidation and invalidation check in subtree.
+  // The points do *not* account for composited scrolling. See
+  // LayoutObject::adjustVisualRectForCompositedScrolling().
   LayoutPoint oldLocation;
   LayoutPoint newLocation;
 };
@@ -90,9 +99,8 @@ class PaintInvalidator {
       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&);