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

ui/gfx/vector2d.cc

Index: ui/gfx/vector2d.cc
diff --git a/ui/gfx/vector2d.cc b/ui/gfx/vector2d.cc
new file mode 100644
index 0000000000000000000000000000000000000000..a1492cbd119be73e6e5a02b20848d5c139d5ea6a
--- /dev/null
+++ b/ui/gfx/vector2d.cc
@@ -0,0 +1,45 @@
+// 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::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 static_cast<int64>(x_) * x_ + static_cast<int64>(y_) * y_;
+}
+
+float Vector2d::Length() const {
+  return static_cast<float>(std::sqrt(static_cast<double>(LengthSquared())));
+}
+
+std::string Vector2d::ToString() const {
+  return base::StringPrintf("[%d %d]", x_, y_);
+}
+
+}  // namespace gfx