Mac: Enable partial swap

ui/gfx/geometry/rect_f.h

Index: ui/gfx/geometry/rect_f.h
diff --git a/ui/gfx/geometry/rect_f.h b/ui/gfx/geometry/rect_f.h
index dc233a77154a37c9424d3e305783e90f51d84fdf..3b132667e40d321f3b0e6b0d74c1495612844af7 100644
--- a/ui/gfx/geometry/rect_f.h
+++ b/ui/gfx/geometry/rect_f.h
@@ -12,6 +12,10 @@
 #include "ui/gfx/geometry/size_f.h"
 #include "ui/gfx/geometry/vector2d_f.h"
 
+#if defined(OS_MACOSX)
+typedef struct CGRect CGRect;
+#endif
+
 namespace gfx {
 
 class InsetsF;
@@ -27,6 +31,12 @@ class GFX_EXPORT RectF {
   RectF(const PointF& origin, const SizeF& size)
       : origin_(origin), size_(size) {}
 
+#if defined(OS_MACOSX)
+  explicit RectF(const CGRect& r);
+  // Construct an equivalent CoreGraphics object.
+  CGRect ToCGRect() const;
+#endif
+
   ~RectF() {}
 
   float x() const { return origin_.x(); }