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 908 matching lines @@
   // 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 {
+    DCHECK(!RuntimeEnabledFeatures::slimmingPaintInvalidationEnabled());
     return previous_painting_clip_rects_.Get();
   }
   void SetPreviousPaintingClipRects(ClipRects& clip_rects) {
     previous_painting_clip_rects_ = &clip_rects;
   }
   void ClearPreviousPaintingClipRects() {
     previous_painting_clip_rects_.Clear();
   }
 
   LayoutRect PreviousPaintDirtyRect() const {
@@ skipping 339 matching lines @@
 
 }  // 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