Add Vector2d classes that represent offsets, instead of using Point.

ui/gfx/rect.h

Index: ui/gfx/rect.h
diff --git a/ui/gfx/rect.h b/ui/gfx/rect.h
index 2eab239d4bc76d948c93b86606622841fe778b39..f43016f3e53bde49dbd21909c2dd5bf9e0714d95 100644
--- a/ui/gfx/rect.h
+++ b/ui/gfx/rect.h
@@ -18,6 +18,7 @@
 #include "ui/gfx/rect_base.h"
 #include "ui/gfx/rect_f.h"
 #include "ui/gfx/size.h"
+#include "ui/gfx/vector2d.h"
 
 #if defined(OS_WIN)
 typedef struct tagRECT RECT;
@@ -33,7 +34,8 @@ namespace gfx {
 
 class Insets;
 
-class UI_EXPORT Rect : public RectBase<Rect, Point, Size, Insets, int> {
+class UI_EXPORT Rect
+    : public RectBase<Rect, Point, Size, Insets, Vector2d, int> {
  public:
   Rect();
   Rect(int width, int height);
@@ -76,7 +78,7 @@ inline bool operator!=(const Rect& lhs, const Rect& rhs) {
 }
 
 #if !defined(COMPILER_MSVC)
-extern template class RectBase<Rect, Point, Size, Insets, int>;
+extern template class RectBase<Rect, Point, Size, Insets, Vector2d, int>;
 #endif
 
 }  // namespace gfx