Generate scroll/clip display item hierarchy for SPv2

Source/core/layout/compositing/CompositedDeprecatedPaintLayerMapping.cpp

 /*
  * Copyright (C) 2009, 2010, 2011 Apple Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 2087 matching lines @@
 
     IntSize offset = paintInfo.offsetFromLayoutObject;
     AffineTransform translation;
     translation.translate(-offset.width(), -offset.height());
     TransformRecorder transformRecorder(*context, *this, translation);
 
     // The dirtyRect is in the coords of the painting root.
     IntRect dirtyRect(clip);
     dirtyRect.move(offset);
 
-    if (!(paintLayerFlags & PaintLayerPaintingOverflowContents)) {
+    if (!(paintLayerFlags & PaintLayerPaintingOverflowContents) && !RuntimeEnabledFeatures::slimmingPaintV2Enabled()) {

[chrishtr, 2015/09/17 00:53:46]

Why this change?

[trchen, 2015/09/17 01:56:04]

In rootLayerScrolls-mode the composited bounds will be the size of the viewport
because LayoutView clip and scrolls the document. Our interest rect will
incorrectly cropped in that case.

In normal mode this is no-op.

[chrishtr, 2015/09/17 18:07:53]

What does this have to do with this CL? 

Furthermore, interest rects will be managed by Blink, not cc, in v2, so all the
code in this file will be obsolete.

         LayoutRect bounds = paintInfo.compositedBounds;
         bounds.move(paintInfo.paintLayer->subpixelAccumulation());
         dirtyRect.intersect(pixelSnappedIntRect(bounds));
     } else {
         dirtyRect.move(roundedIntSize(paintInfo.paintLayer->subpixelAccumulation()));
     }
 
 #if ENABLE(ASSERT)
     paintInfo.paintLayer->layoutObject()->assertSubtreeIsLaidOut();
 #endif
@@ skipping 265 matching lines @@
     } else if (graphicsLayer == m_scrollingBlockSelectionLayer.get()) {
         name = "Scrolling Block Selection Layer";
     } else {
         ASSERT_NOT_REACHED();
     }
 
     return name;
 }
 
 } // namespace blink