Reland of Client side display item cache flag

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

 /*
  * Copyright (C) 2006, 2007, 2008, 2009, 2010, 2011, 2012 Apple Inc. 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>
  *   Randall Jesup <rjesup@wgate.com>
@@ skipping 95 matching lines @@
     Persistent<PaintLayerScrollableArea> scrollableArea;
     struct {
         IntRect rect;
         void* pointers[2];
     } ancestorCompositingInputs;
     struct {
         IntSize size;
         void* pointer;
         LayoutRect rect;
     } previousPaintStatus;
+    DisplayItemCacheGeneration cacheGeneration;
 };
 
 static_assert(sizeof(PaintLayer) == sizeof(SameSizeAsPaintLayer), "PaintLayer should stay small");
 
 } // namespace
 
 using namespace HTMLNames;
 
 PaintLayerRareData::PaintLayerRareData()
     : enclosingPaginationLayer(nullptr)
@@ skipping 2786 matching lines @@
 
 void showLayerTree(const blink::LayoutObject* layoutObject)
 {
     if (!layoutObject) {
         fprintf(stderr, "Cannot showLayerTree. Root is (nil)\n");
         return;
     }
     showLayerTree(layoutObject->enclosingLayer());
 }
 #endif