Calculate correct clip foregroundBound and backgroundBound

Source/core/paint/DeprecatedPaintLayerClipper.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 209 matching lines @@
         backgroundRect.move(roundedIntSize(context.subPixelAccumulation));
         backgroundRect.intersect(paintDirtyRect);
     } else {
         backgroundRect = paintDirtyRect;
     }
 
     foregroundRect = backgroundRect;
     outlineRect = backgroundRect;
 
     LayoutPoint offset;
-    if (offsetFromRoot)
+    if (offsetFromRoot) {
         offset = *offsetFromRoot;
-    else
+        foregroundRect.move(context.subPixelAccumulation);

[pdr., 2015/08/07 23:20:31]

Why don't we need to move backgroundRect too?

[qiankun, 2015/08/13 10:36:03]

Thanks for review. backgroundRect also needs to move. I updated the CL. Layout
test was added.  

+        outlineRect.move(context.subPixelAccumulation);
+    } else {
         m_layoutObject.layer()->convertToLayerCoords(context.rootLayer, offset);
+    }
     layerBounds = LayoutRect(offset, LayoutSize(m_layoutObject.layer()->size()));
 
     // Update the clip rects that will be passed to child layers.
     if (m_layoutObject.hasOverflowClip()) {
         // This layer establishes a clip of some kind.
         if (shouldRespectOverflowClip(context)) {
             foregroundRect.intersect(toLayoutBox(m_layoutObject).overflowClipRect(offset, context.scrollbarRelevancy));
             if (m_layoutObject.style()->hasBorderRadius())
                 foregroundRect.setHasRadius(true);
         }
@@ skipping 139 matching lines @@
     if (context.respectOverflowClip == IgnoreOverflowClip)
         return false;
 
     if (layer->isRootLayer() && context.respectOverflowClipForViewport == IgnoreOverflowClip)
         return false;
 
     return true;
 }
 
 } // namespace blink