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

ui/gfx/point_base.h

 // 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.
 
 #ifndef UI_GFX_POINT_BASE_H_
 #define UI_GFX_POINT_BASE_H_
 
 #include <string>
 
 #include "base/compiler_specific.h"
 #include "build/build_config.h"
 #include "ui/base/ui_export.h"
 
 namespace gfx {
 
 // A point has an x and y coordinate.
-template<typename Class, typename Type>
+template<typename Class, typename Type, typename VectorClass>
 class UI_EXPORT PointBase {
  public:
   Type x() const { return x_; }
   Type y() const { return y_; }
 
   void SetPoint(Type x, Type y) {
     x_ = x;
     y_ = y;
   }
 
   void set_x(Type x) { x_ = x; }
   void set_y(Type y) { y_ = y; }
 
   void Offset(Type delta_x, Type delta_y) {
     x_ += delta_x;
     y_ += delta_y;
   }
 
-  Class Add(const Class& other) const WARN_UNUSED_RESULT {
+  Class Add(const VectorClass& other) const WARN_UNUSED_RESULT {
     const Class* orig = static_cast<const Class*>(this);
     Class copy = *orig;
-    copy.Offset(other.x_, other.y_);
+    copy.Offset(other.x(), other.y());
     return copy;
   }
 
-  Class Subtract(const Class& other) const WARN_UNUSED_RESULT {
+  Class Subtract(const VectorClass& other) const WARN_UNUSED_RESULT {
     const Class* orig = static_cast<const Class*>(this);
     Class copy = *orig;
-    copy.Offset(-other.x_, -other.y_);
+    copy.Offset(-other.x(), -other.y());
     return copy;
   }
 
   Class Middle(const Class& other) const WARN_UNUSED_RESULT {
     return Class((x_ + other.x_) / 2, (y_ + other.y_) / 2);
   }
 
   bool IsOrigin() const {
     return x_ == 0 && y_ == 0;
   }
 
+  VectorClass DistanceFromOrigin() const {
+    return VectorClass(x_, y_);
+  }
+
+  VectorClass DistanceFrom(const Class& other) const {
+    return VectorClass(x_ - other.x_, y_ - other.y_);
+  }
+
   // A point is less than another point if its y-value is closer
   // to the origin. If the y-values are the same, then point with
   // the x-value closer to the origin is considered less than the
   // other.
   // This comparison is required to use Point in sets, or sorted
   // vectors.
   bool operator<(const Class& rhs) const {
     return (y_ == rhs.y_) ? (x_ < rhs.x_) : (y_ < rhs.y_);
   }
 
  protected:
   PointBase(Type x, Type y) : x_(x), y_(y) {}
   // Destructor is intentionally made non virtual and protected.
   // Do not make this public.
   ~PointBase() {}
 
  private:
   Type x_;
   Type y_;
 };
 
 }  // namespace gfx
 
 #endif  // UI_GFX_POINT_BASE_H_