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

ash/display/multi_display_manager.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/display/multi_display_manager.h"
 
 #include <string>
 #include <vector>
 
 #include "ash/display/display_controller.h"
@@ skipping 322 matching lines @@
 const gfx::Display& MultiDisplayManager::GetDisplayMatching(
     const gfx::Rect& rect) const {
   if (rect.IsEmpty())
     return GetDisplayNearestPoint(rect.origin());
 
   int max = 0;
   const gfx::Display* matching = 0;
   for (std::vector<gfx::Display>::const_iterator iter = displays_.begin();
        iter != displays_.end(); ++iter) {
     const gfx::Display& display = *iter;
-    gfx::Rect intersect = display.bounds().Intersect(rect);
+    gfx::Rect intersect = display.bounds();
+    intersect.Intersect(rect);
     int area = intersect.width() * intersect.height();
     if (area > max) {
       max = area;
       matching = &(*iter);
     }
   }
   // Fallback to the primary display if there is no matching display.
   return matching ? *matching : DisplayController::GetPrimaryDisplay();
 }
 
@@ skipping 129 matching lines @@
   DisplayList::iterator iter_to_update = to_update->begin();
   DisplayList::const_iterator iter = displays_.begin();
   for (; iter != displays_.end() && iter_to_update != to_update->end();
        ++iter, ++iter_to_update) {
     (*iter_to_update).set_id((*iter).id());
   }
 }
 
 }  // namespace internal
 }  // namespace ash