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

ui/compositor/layer.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/compositor/layer.h"
 
 #include <algorithm>
 
 #include "base/command_line.h"
 #include "base/debug/trace_event.h"
@@ skipping 445 matching lines @@
          !iter.done(); iter.next()) {
       const SkIRect& sk_damaged = iter.rect();
       gfx::Rect damaged(
           sk_damaged.x(),
           sk_damaged.y(),
           sk_damaged.width(),
           sk_damaged.height());
 
       if (scale_content_ && web_layer_is_accelerated_) {
         damaged.Inset(-1, -1);
-        damaged = damaged.Intersect(gfx::Rect(bounds_.size()));
+        damaged.Intersect(gfx::Rect(bounds_.size()));
       }
 
       gfx::Rect damaged_in_pixel = ConvertRectToPixel(this, damaged);
       WebKit::WebFloatRect web_rect(
           damaged_in_pixel.x(),
           damaged_in_pixel.y(),
           damaged_in_pixel.width(),
           damaged_in_pixel.height());
       web_layer_->invalidateRect(web_rect);
     }
@@ skipping 301 matching lines @@
     return;
   unsigned int color = 0xFF000000;
   color |= web_layer_is_accelerated_ ? 0x0000FF00 : 0x00FF0000;
   bool opaque = fills_bounds_opaquely_ && (GetCombinedOpacity() == 1.f);
   if (!opaque)
     color |= 0xFF;
   web_layer_->setDebugBorderColor(color);
 }
 
 }  // namespace ui