Make gfx::Rect class operations consistently mutate the class they are called on.

ui/gfx/rect_f.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_RECT_F_H_
 #define UI_GFX_RECT_F_H_
 
 #include <string>
 
 #include "ui/gfx/point_f.h"
 #include "ui/gfx/rect_base.h"
 #include "ui/gfx/size_f.h"
 
 namespace gfx {
 
 class InsetsF;
 
 // A floating version of gfx::Rect.
 class UI_EXPORT RectF : public RectBase<RectF, PointF, SizeF, InsetsF, float> {
  public:
   RectF();
   RectF(float width, float height);
   RectF(float x, float y, float width, float height);
   explicit RectF(const gfx::SizeF& size);
   RectF(const gfx::PointF& origin, const gfx::SizeF& size);
 
   ~RectF();
 
   /// Scales the rectangle by |scale|.
-  RectF Scale(float scale) const WARN_UNUSED_RESULT {
-    return Scale(scale, scale);
+  void Scale(float scale) {
+    Scale(scale, scale);
   }
 
-  RectF Scale(float x_scale, float y_scale) const WARN_UNUSED_RESULT {
+  void Scale(float x_scale, float y_scale) {
     SizeF newSize = size().Scale(x_scale, y_scale);
     newSize.ClampToNonNegative();
-    return RectF(origin().Scale(x_scale, y_scale), newSize);
+    set_origin(origin().Scale(x_scale, y_scale));
+    set_size(newSize);
   }
 
   std::string ToString() const;
 };
 
 inline bool operator==(const RectF& lhs, const RectF& rhs) {
   return lhs.origin() == rhs.origin() && lhs.size() == rhs.size();
 }
 
 inline bool operator!=(const RectF& lhs, const RectF& rhs) {
   return !(lhs == rhs);
 }
 
 #if !defined(COMPILER_MSVC)
 extern template class RectBase<RectF, PointF, SizeF, InsetsF, float>;
 #endif
 
 }  // namespace gfx
 
 #endif  // UI_GFX_RECT_F_H_