ui: Prefer +/- operators to apply offsets.

ui/gfx/rect_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.
 
 // A template for a simple rectangle class.  The containment semantics
 // are array-like; that is, the coordinate (x, y) is considered to be
 // contained by the rectangle, but the coordinate (x + width, y) is not.
 // The class will happily let you create malformed rectangles (that is,
 // rectangles with negative width and/or height), but there will be assertions
 // in the operations (such as Contains()) to complain in this case.
@@ skipping 51 matching lines @@
   void Inset(const InsetsClass& insets);
 
   // Shrink the rectangle by the specified amount on each side.
   void Inset(Type left, Type top, Type right, Type bottom);
 
   // Move the rectangle by a horizontal and vertical distance.
   void Offset(Type horizontal, Type vertical);
   void Offset(const VectorClass& distance) {
     Offset(distance.x(), distance.y());
   }
+  void operator+=(const VectorClass& offset);
+  void operator-=(const VectorClass& offset);
 
   InsetsClass InsetsFrom(const Class& inner) const {
     return InsetsClass(inner.y() - y(),
                        inner.x() - x(),
                        bottom() - inner.bottom(),
                        right() - inner.right());
   }
 
   // Returns true if the area of the rectangle is zero.
   bool IsEmpty() const { return size_.IsEmpty(); }
@@ skipping 65 matching lines @@
   ~RectBase();
 
  private:
   PointClass origin_;
   SizeClass size_;
 };
 
 }  // namespace gfx
 
 #endif  // UI_GFX_RECT_BASE_H_