ui: Make gfx::Size::Scale() mutate the class. Add gfx::ScaleSize() similar to Rect/Point.

ui/gfx/size_f.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/size_f.h"
 
 #include "base/logging.h"
 #include "base/stringprintf.h"
 
 namespace gfx {
 
 template class SizeBase<SizeF, float>;
 
 SizeF::SizeF() : SizeBase<SizeF, float>(0, 0) {}
 
 SizeF::SizeF(float width, float height) : SizeBase<SizeF, float>(0, 0) {
   set_width(width);
   set_height(height);
 }
 
 SizeF::~SizeF() {}
 
 std::string SizeF::ToString() const {
   return base::StringPrintf("%fx%f", width(), height());
 }
 
+SizeF ScaleSize(const SizeF& s, float x_scale, float y_scale) {
+  SizeF scaled_s(s);
+  scaled_s.Scale(x_scale, y_scale);
+  return scaled_s;
+}
+
 }  // namespace gfx