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

ui/gfx/vector2d_f.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-#include "ui/gfx/insets_f.h"
-
 #include "base/stringprintf.h"
+#include "ui/gfx/vector2d_f.h"
 
 namespace gfx {
 
-std::string InsetsF::ToString() const {
-  // Print members in the same order of the constructor parameters.
-  return StringPrintf("%f,%f,%f,%f", top_,  left_, bottom_, right_);
+Vector2dF::Vector2dF()
+    : x_(0),
+      y_(0) {
+}
+
+Vector2dF::Vector2dF(float x, float y)
+    : x_(x),
+      y_(y) {
+}
+
+std::string Vector2dF::ToString() const {
+  return base::StringPrintf("[%f %f]", x_, y_);
 }
 
 }  // namespace gfx