Reland of duce copying of local data structures in GeometryMapper and PaintLayerClipper.

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

Index: third_party/WebKit/Source/core/paint/ClipRect.h
diff --git a/third_party/WebKit/Source/core/paint/ClipRect.h b/third_party/WebKit/Source/core/paint/ClipRect.h
index d1b13ab96c3d8e420f4e3af75ae4b0581b0bed0e..0770bcb82ce2ac020a2a3758001561ed2a5b1c83 100644
--- a/third_party/WebKit/Source/core/paint/ClipRect.h
+++ b/third_party/WebKit/Source/core/paint/ClipRect.h
@@ -43,7 +43,12 @@
   ClipRect(const LayoutRect& rect) : m_rect(rect), m_hasRadius(false) {}
 
   ClipRect(const FloatClipRect& rect)
-      : m_rect(LayoutRect(rect.rect())), m_hasRadius(rect.hasRadius()) {}
+      : m_rect(rect.rect()), m_hasRadius(rect.hasRadius()) {}
+
+  void setRect(const FloatClipRect& rect) {
+    m_rect = LayoutRect(rect.rect());
+    m_hasRadius = rect.hasRadius();
+  }
 
   const LayoutRect& rect() const { return m_rect; }