Add non-member non-mutating methods for common gfx::Rect operations.

ash/wm/workspace/workspace_window_resizer.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/wm/workspace/workspace_window_resizer.h"
 
 #include <algorithm>
 #include <cmath>
 #include <utility>
 #include <vector>
@@ skipping 670 matching lines @@
       !ShouldAllowMouseWarp()) {
     return;
   }
 
   // It's available. Show a phantom window on the display if needed.
   aura::RootWindow* another_root =
       GetAnotherRootWindow(window()->GetRootWindow());
   const gfx::Rect root_bounds_in_screen(another_root->GetBoundsInScreen());
   const gfx::Rect bounds_in_screen =
       ScreenAsh::ConvertRectToScreen(window()->parent(), bounds);
-  gfx::Rect bounds_in_another_root = root_bounds_in_screen;
-  bounds_in_another_root.Intersect(bounds_in_screen);
+  gfx::Rect bounds_in_another_root =
+      gfx::Intersection(root_bounds_in_screen, bounds_in_screen);
 
   const float fraction_in_another_window =
       (bounds_in_another_root.width() * bounds_in_another_root.height()) /
       static_cast<float>(bounds.width() * bounds.height());
   const float phantom_opacity =
       !in_original_root ? 1 : (kMaxOpacity * fraction_in_another_window);
   const float window_opacity =
       in_original_root ? 1 : (kMaxOpacity * (1 - fraction_in_another_window));
 
   if (fraction_in_another_window > 0) {
@@ skipping 106 matching lines @@
   gfx::Rect layer_bounds = layer_->bounds();
   layer_bounds.set_origin(gfx::Point(0, 0));
   layer_->SetBounds(layer_bounds);
   layer_->SetVisible(false);
   // Detach it from the current container.
   layer_->parent()->Remove(layer_);
 }
 
 }  // namespace internal
 }  // namespace ash