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

ui/gfx/point_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/point_f.h"
 
 #include "base/stringprintf.h"
 
 namespace gfx {
 
-template class PointBase<PointF, float>;
+template class PointBase<PointF, float, Vector2dF>;
 
-PointF::PointF() : PointBase<PointF, float>(0, 0) {
+PointF::PointF() : PointBase<PointF, float, Vector2dF>(0, 0) {
 }
 
-PointF::PointF(float x, float y) : PointBase<PointF, float>(x, y) {
+PointF::PointF(float x, float y) : PointBase<PointF, float, Vector2dF>(x, y) {
 }
 
 PointF::~PointF() {}
 
 std::string PointF::ToString() const {
   return base::StringPrintf("%f,%f", x(), y());
 }
 
 }  // namespace gfx