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

ui/views/widget/native_widget_aura.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/views/widget/native_widget_aura.h"
 
 #include "base/bind.h"
 #include "base/string_util.h"
 #include "third_party/skia/include/core/SkRegion.h"
 #include "ui/aura/client/activation_change_observer.h"
@@ skipping 278 matching lines @@
 
   aura::client::ScreenPositionClient* screen_position_client =
       aura::client::GetScreenPositionClient(window_->GetRootWindow());
   if (screen_position_client) {
     gfx::Point origin = work_area.origin();
     screen_position_client->ConvertPointFromScreen(window_->GetRootWindow(),
                                                    &origin);
     work_area.set_origin(origin);
   }
 
-  parent_bounds = parent_bounds.Intersect(work_area);
+  parent_bounds.Intersect(work_area);
 
   // If |window_|'s transient parent's bounds are big enough to fit it, then we
   // center it with respect to the transient parent.
   if (window_->transient_parent()) {
     gfx::Rect transient_parent_rect = window_->transient_parent()->
         GetBoundsInRootWindow().Intersect(work_area);
     if (transient_parent_rect.height() >= size.height() &&
         transient_parent_rect.width() >= size.width())
       parent_bounds = transient_parent_rect;
   }
@@ skipping 694 matching lines @@
   return aura::Env::GetInstance()->is_mouse_button_down();
 }
 
 // static
 bool NativeWidgetPrivate::IsTouchDown() {
   return aura::Env::GetInstance()->is_touch_down();
 }
 
 }  // namespace internal
 }  // namespace views