Store previous painting clip rects on FragmentData.

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

 /*
  * Copyright (C) 2003, 2009, 2012 Apple Inc. All rights reserved.
  * Copyright (C) 2013 Intel Corporation. All rights reserved.
  *
  * Portions are Copyright (C) 1998 Netscape Communications Corporation.
  *
  * Other contributors:
  *   Robert O'Callahan <roc+@cs.cmu.edu>
  *   David Baron <dbaron@fas.harvard.edu>
  *   Christian Biesinger <cbiesinger@web.de>
@@ skipping 907 matching lines @@
   // shouldCreateSubsequence() in PaintLayerPainter.cpp for the cases we use
   // subsequence when painting a PaintLayer.
 
   IntSize PreviousScrollOffsetAccumulationForPainting() const {
     return previous_scroll_offset_accumulation_for_painting_;
   }
   void SetPreviousScrollOffsetAccumulationForPainting(const IntSize& s) {
     previous_scroll_offset_accumulation_for_painting_ = s;
   }
 
-  ClipRects* PreviousPaintingClipRects() const {
-    return previous_painting_clip_rects_.Get();
+  ClipRects* PreviousClipRects() const {
+    DCHECK(!RuntimeEnabledFeatures::slimmingPaintInvalidationEnabled());
+    return previous_clip_rects_.Get();
   }
-  void SetPreviousPaintingClipRects(ClipRects& clip_rects) {
-    previous_painting_clip_rects_ = &clip_rects;
+  void SetPreviousClipRects(ClipRects& clip_rects) {
+    previous_clip_rects_ = &clip_rects;

[wkorman, 2017/05/01 21:58:09]

Will this do the right thing re: RefPtr? I'd think we have to pass PassRefPtr as
param for the counting to do what's intended.

My concern is re: who owns the memory allocated for the inputted clip_rects. Do
we have any assurance the caller won't deallocate but we'll keep our ref here.

But I actually couldn't find any documentation on PassRefPtr or RefPtr just now
when I looked.

[chrishtr, 2017/05/01 22:40:07]

The memory is owned by the PaintLayer or FragmentData. It does work but I agree
it's a bit
weird looking. I had to research it when I first found it also.

   }
-  void ClearPreviousPaintingClipRects() {
-    previous_painting_clip_rects_.Clear();
-  }
+  void ClearPreviousClipRects() { previous_clip_rects_.Clear(); }
 
   LayoutRect PreviousPaintDirtyRect() const {
     return previous_paint_dirty_rect_;
   }
   void SetPreviousPaintDirtyRect(const LayoutRect& rect) {
     previous_paint_dirty_rect_ = rect;
   }
 
   PaintResult PreviousPaintResult() const {
     return static_cast<PaintResult>(previous_paint_result_);
@@ skipping 311 matching lines @@
   std::unique_ptr<AncestorDependentCompositingInputs>
       ancestor_dependent_compositing_inputs_;
 
   Persistent<PaintLayerScrollableArea> scrollable_area_;
 
   mutable std::unique_ptr<ClipRectsCache> clip_rects_cache_;
 
   std::unique_ptr<PaintLayerStackingNode> stacking_node_;
 
   IntSize previous_scroll_offset_accumulation_for_painting_;
-  RefPtr<ClipRects> previous_painting_clip_rects_;
+  RefPtr<ClipRects> previous_clip_rects_;
   LayoutRect previous_paint_dirty_rect_;
 
   std::unique_ptr<PaintLayerRareData> rare_data_;
 
   FRIEND_TEST_ALL_PREFIXES(PaintLayerTest,
                            DescendantDependentFlagsStopsAtThrottledFrames);
   FRIEND_TEST_ALL_PREFIXES(PaintLayerTest,
                            PaintLayerTransformUpdatedOnStyleTransformAnimation);
 };
 
 }  // namespace blink
 
 #ifndef NDEBUG
 // Outside the WebCore namespace for ease of invocation from gdb.
 CORE_EXPORT void showLayerTree(const blink::PaintLayer*);
 CORE_EXPORT void showLayerTree(const blink::LayoutObject*);
 #endif
 
 #endif  // Layer_h