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

chrome/browser/notifications/balloon_collection_impl.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 "chrome/browser/notifications/balloon_collection_impl.h"
 
 #include "base/bind.h"
 #include "base/logging.h"
 #include "base/stl_util.h"
 #include "chrome/browser/notifications/balloon.h"
@@ skipping 200 matching lines @@
   // Start from the layout origin.
   gfx::Rect bounds = gfx::Rect(layout_.GetLayoutOrigin(), gfx::Size(0, 0));
 
   // For each balloon, extend the rectangle.  This approach is indifferent to
   // the orientation of the balloons.
   const Balloons& balloons = base_.balloons();
   Balloons::const_iterator iter;
   for (iter = balloons.begin(); iter != balloons.end(); ++iter) {
     gfx::Rect balloon_box = gfx::Rect((*iter)->GetPosition(),
                                       (*iter)->GetViewSize());
-    bounds = bounds.Union(balloon_box);
+    bounds.Union(balloon_box);
   }
 
   return bounds;
 }
 
 #if USE_OFFSETS
 void BalloonCollectionImpl::AddMessageLoopObserver() {
   if (!added_as_message_loop_observer_) {
     MessageLoopForUI::current()->AddObserver(this);
     added_as_message_loop_observer_ = true;
@@ skipping 238 matching lines @@
       gfx::Screen::GetNativeScreen()->GetPrimaryDisplay().work_area();
 #endif
   if (work_area_ != new_work_area) {
     work_area_.SetRect(new_work_area.x(), new_work_area.y(),
                        new_work_area.width(), new_work_area.height());
     changed = true;
   }
 
   return changed;
 }