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

ui/gfx/vector2d.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/vector2d.h"
+
+#include <cmath>
+
+#include "base/stringprintf.h"
+
+namespace gfx {
+
+Vector2d::Vector2d()
+    : x_(0),
+      y_(0) {
+}
+
+Vector2d::Vector2d(int x, int y)
+    : x_(x),
+      y_(y) {
+}
+
+bool Vector2d::IsZero() const {
+  return x_ == 0 && y_ == 0;
+}
+
+void Vector2d::Grow(int x, int y) {
+  x_ += x;
+  y_ += y;
+}
+
+void Vector2d::Add(const Vector2d& other) {
+  x_ += other.x_;
+  y_ += other.y_;
+}
+
+void Vector2d::Subtract(const Vector2d& other) {
+  x_ -= other.x_;
+  y_ -= other.y_;
+}
+
+int64 Vector2d::LengthSquared() const {
+  return x_ * x_ + y_ * y_;
+}
+
+float Vector2d::Length() const {
+  return static_cast<float>(std::sqrt(
+      static_cast<double>(x_) * x_ + static_cast<double>(y_) * y_));
+}
+
+std::string Vector2d::ToString() const {
+  return base::StringPrintf("[%d %d]", x_, y_);
+}
+
+}  // namespace gfx