SPv2: Use GeometryMapper to implement PaintLayerClipper.

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

Index: third_party/WebKit/Source/core/paint/PaintLayer.h
diff --git a/third_party/WebKit/Source/core/paint/PaintLayer.h b/third_party/WebKit/Source/core/paint/PaintLayer.h
index 1fe75502941ff79698d21c7cea3cb5d73970b4ac..0d91b02867262c9016d0f1ee39703466e7af6fea 100644
--- a/third_party/WebKit/Source/core/paint/PaintLayer.h
+++ b/third_party/WebKit/Source/core/paint/PaintLayer.h
@@ -614,7 +614,10 @@ class CORE_EXPORT PaintLayer : public DisplayItemClient {
     return m_scrollableArea.get();
   }
 
-  PaintLayerClipper clipper() const { return PaintLayerClipper(*this); }
+  PaintLayerClipper clipper() const {
+    return PaintLayerClipper(*this,
+                             RuntimeEnabledFeatures::slimmingPaintV2Enabled());
+  }
 
   bool scrollsOverflow() const;