Store previous painting clip rects on FragmentData.

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

Index: third_party/WebKit/Source/core/paint/PrePaintTreeWalk.h
diff --git a/third_party/WebKit/Source/core/paint/PrePaintTreeWalk.h b/third_party/WebKit/Source/core/paint/PrePaintTreeWalk.h
index 4e6e9893d6ea7ae5f42a8c24e88a269a6ffc2717..ea80c3c316c912c9a8d67c05560409cd7c941c54 100644
--- a/third_party/WebKit/Source/core/paint/PrePaintTreeWalk.h
+++ b/third_party/WebKit/Source/core/paint/PrePaintTreeWalk.h
@@ -19,7 +19,7 @@ struct PrePaintTreeWalkContext;
 // This class walks the whole layout tree, beginning from the root FrameView,
 // across frame boundaries. Helper classes are called for each tree node to
 // perform actual actions.  It expects to be invoked in InPrePaint phase.
-class PrePaintTreeWalk {
+class CORE_EXPORT PrePaintTreeWalk {
  public:
   PrePaintTreeWalk() {}
   void Walk(FrameView& root_frame);
@@ -34,6 +34,13 @@ class PrePaintTreeWalk {
       const LayoutObject&,
       PrePaintTreeWalkContext&);
 
+  // Returns true if we should force checking subtree invalidation flags.
+  ALWAYS_INLINE bool InvalidatePaintLayerOptimizationsForFragment(
+      const LayoutObject&,
+      const PaintLayer* ancestor_transformed_or_root_paint_layer,
+      const PaintPropertyTreeBuilderFragmentContext&,
+      FragmentData&);
+
   // Returns the clip applied to children for the given containing block context
   // + effect, in the space of ancestorState adjusted by ancestorPaintOffset.
   ALWAYS_INLINE LayoutRect ComputeClipRectForContext(
@@ -49,8 +56,12 @@ class PrePaintTreeWalk {
   NeedsTreeBuilderContextUpdate(const LayoutObject&,
                                 const PrePaintTreeWalkContext&);
 
+  static void ClearPreviousClipRectsForTesting(const LayoutObject&);
+
   PaintPropertyTreeBuilder property_tree_builder_;
   PaintInvalidator paint_invalidator_;
+
+  FRIEND_TEST_ALL_PREFIXES(PrePaintTreeWalkTest, ClipRects);
 };
 
 }  // namespace blink