Generate scroll/clip display item hierarchy for SPv2

Source/core/paint/DeprecatedPaintLayer.h

Index: Source/core/paint/DeprecatedPaintLayer.h
diff --git a/Source/core/paint/DeprecatedPaintLayer.h b/Source/core/paint/DeprecatedPaintLayer.h
index 032cdf2cdc32e74828f97b9bcf3e0f9a023b7217..63445a6946ab917261374263d3efeb7273452f29 100644
--- a/Source/core/paint/DeprecatedPaintLayer.h
+++ b/Source/core/paint/DeprecatedPaintLayer.h
@@ -142,7 +142,15 @@ public:
         return curr;
     }
 
-    const LayoutPoint& location() const { ASSERT(!m_needsPositionUpdate); return m_location; }
+    enum LocationQueryBehavior {
+        IncludeScroll,
+        ExcludeScroll
+    };
+    LayoutPoint location(LocationQueryBehavior behavior = IncludeScroll) const { ASSERT(!m_needsPositionUpdate); return behavior == IncludeScroll ? m_location : locationExcludeOverflowScroll(); }
+    // Note: This function is only needed during the transition period to SPv2.
+    // Once we have eliminated layer-based hit testing and clipping,
+    // we can cache the unscrolled location instead.
+    LayoutPoint locationExcludeOverflowScroll() const;

[jbroman, 2015/09/09 19:58:30]

nit: "locationExcludingOverflowScroll", please? I initially read this as
"locationExcludesOverflowScroll" and wondered why it didn't return a boolean.

[trchen, 2015/09/15 04:48:40]

Done.

     // FIXME: size() should ASSERT(!m_needsPositionUpdate) as well, but that fails in some tests,
     // for example, fast/repaint/clipped-relative.html.
     const IntSize& size() const { return m_size; }
@@ -227,7 +235,7 @@ public:
         return !layoutObject()->hasTransformRelatedProperty() && !layoutObject()->isSVGRoot();
     }
 
-    void convertToLayerCoords(const DeprecatedPaintLayer* ancestorLayer, LayoutPoint&) const;
+    void convertToLayerCoords(const DeprecatedPaintLayer* ancestorLayer, LayoutPoint&, LocationQueryBehavior = IncludeScroll) const;
     void convertToLayerCoords(const DeprecatedPaintLayer* ancestorLayer, LayoutRect&) const;
 
     // Does the same as convertToLayerCoords() when not in multicol. For multicol, however,