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

ash/desktop_background/desktop_background_view.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 "ash/desktop_background/desktop_background_view.h"
 
 #include <limits>
 
 #include "ash/ash_export.h"
 #include "ash/desktop_background/desktop_background_controller.h"
@@ skipping 109 matching lines @@
     gfx::Size cropped_size;
     if (vertical_ratio > horizontal_ratio) {
       cropped_size = gfx::Size(
           RoundPositive(static_cast<double>(width()) / vertical_ratio),
           wallpaper.height());
     } else {
       cropped_size = gfx::Size(wallpaper.width(),
           RoundPositive(static_cast<double>(height()) / horizontal_ratio));
     }
 
-    gfx::Rect wallpaper_cropped_rect = wallpaper_rect.Center(cropped_size);
+    gfx::Rect wallpaper_cropped_rect = wallpaper_rect;
+    wallpaper_cropped_rect.ClampToCenteredSize(cropped_size);
     canvas->DrawImageInt(wallpaper,
         wallpaper_cropped_rect.x(), wallpaper_cropped_rect.y(),
         wallpaper_cropped_rect.width(), wallpaper_cropped_rect.height(),
         0, 0, width(), height(),
         true);
   } else if (wallpaper_layout == ash::TILE) {
     canvas->TileImageInt(wallpaper, 0, 0, width(), height());
   } else if (wallpaper_layout == ash::STRETCH) {
     // This is generally not recommended as it may show artifacts.
     canvas->DrawImageInt(wallpaper, 0, 0, wallpaper.width(),
@@ skipping 47 matching lines @@
   settings.SetPreemptionStrategy(ui::LayerAnimator::ENQUEUE_NEW_ANIMATION);
   settings.AddObserver(new ShowWallpaperAnimationObserver(root_window,
                                                           desktop_widget));
   desktop_widget->Show();
   desktop_widget->GetNativeView()->SetName("DesktopBackgroundView");
   return desktop_widget;
 }
 
 }  // namespace internal
 }  // namespace ash