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

ui/base/gestures/gesture_point.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/base/gestures/gesture_point.h"
 
 #include <cmath>
 
 #include "base/basictypes.h"
 #include "ui/base/events/event.h"
@@ skipping 173 matching lines @@
   if (event.radius_x() || event.radius_y())
     radius = std::max(event.radius_x(), event.radius_y());
   else
     radius = GestureConfiguration::default_radius();
 
   gfx::Rect rect(event.location().x() - radius,
                  event.location().y() - radius,
                  radius * 2,
                  radius * 2);
   if (IsInClickWindow(event))
-    enclosing_rect_ = enclosing_rect_.Union(rect);
+    enclosing_rect_.Union(rect);
   else
     enclosing_rect_ = rect;
 }
 
 }  // namespace ui