Ignore overflow clip on root layer if HitTestRequest::IgnoreClipping is set.

Source/core/paint/DeprecatedPaintLayerClipper.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 47 matching lines @@
 };
 
 class ClipRectsContext {
 public:
     ClipRectsContext(const DeprecatedPaintLayer* root, ClipRectsCacheSlot slot, OverlayScrollbarSizeRelevancy relevancy = IgnoreOverlayScrollbarSize, const LayoutSize& accumulation = LayoutSize())
         : rootLayer(root)
         , scrollbarRelevancy(relevancy)
         , cacheSlot(slot)
         , subPixelAccumulation(accumulation)
         , respectOverflowClip(slot == PaintingClipRectsIgnoringOverflowClip ? IgnoreOverflowClip : RespectOverflowClip)
+        , respectOverflowClipForViewport(slot == RootRelativeClipRectsIgnoringViewportClip ? IgnoreOverflowClip : RespectOverflowClip)
     {
     }
 
     void setIgnoreOverflowClip()
     {
         ASSERT(!usesCache() || cacheSlot == PaintingClipRects);
         ASSERT(respectOverflowClip == RespectOverflowClip);
         if (usesCache())
             cacheSlot = PaintingClipRectsIgnoringOverflowClip;
         respectOverflowClip = IgnoreOverflowClip;
     }
 
     bool usesCache() const
     {
         return cacheSlot != UncachedClipRects;
     }
 
     const DeprecatedPaintLayer* const rootLayer;
     const OverlayScrollbarSizeRelevancy scrollbarRelevancy;
 
 private:
     friend class DeprecatedPaintLayerClipper;
 
     ClipRectsCacheSlot cacheSlot;
     LayoutSize subPixelAccumulation;
     ShouldRespectOverflowClip respectOverflowClip;
+    ShouldRespectOverflowClip respectOverflowClipForViewport;
 };
 
 class DeprecatedPaintLayerClipper {
     WTF_MAKE_NONCOPYABLE(DeprecatedPaintLayerClipper);
 public:
     explicit DeprecatedPaintLayerClipper(LayoutBoxModelObject&);
 
     void clearClipRectsIncludingDescendants();
     void clearClipRectsIncludingDescendants(ClipRectsCacheSlot);
 
@@ skipping 28 matching lines @@
 
     DeprecatedPaintLayer* clippingRootForPainting() const;
 
     ClipRectsCache& cache() const
     {
         if (!m_cache)
             m_cache = adoptPtr(new ClipRectsCache);
         return *m_cache;
     }
 
+    bool shouldRespectOverflowClip(const ClipRectsContext&) const;
+
     // FIXME: Could this be a LayoutBox?
     LayoutBoxModelObject& m_layoutObject;
     mutable OwnPtr<ClipRectsCache> m_cache;
 };
 
 } // namespace blink
 
 #endif // LayerClipper_h