Add context to gfx::Screen calls in support of simultaneous desktop+ash

ash/wm/workspace/workspace_manager2_unittest.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_manager2.h"
 
 #include "ash/ash_switches.h"
 #include "ash/screen_ash.h"
 #include "ash/shell.h"
 #include "ash/shell_window_ids.h"
@@ skipping 56 matching lines @@
   aura::Window* GetViewport() {
     return Shell::GetContainer(Shell::GetPrimaryRootWindow(),
                                kShellWindowId_DefaultContainer);
   }
 
   const std::vector<Workspace2*>& workspaces() const {
     return manager_->workspaces_;
   }
 
   gfx::Rect GetFullscreenBounds(aura::Window* window) {
-    return gfx::Screen::GetDisplayNearestWindow(window).bounds();
+    return Shell::GetAshScreen()->GetDisplayNearestWindow(window).bounds();
   }
 
   Workspace2* active_workspace() {
     return manager_->active_workspace_;
   }
 
   Workspace2* FindBy(aura::Window* window) const {
     return manager_->FindBy(window);
   }
 
@@ skipping 1012 matching lines @@
   EXPECT_EQ(w1->parent(), w2->parent());
   ASSERT_EQ("0 M2 active=1", StateString());
 
   // Activate |w1|, should result in dropping |w2| to the desktop.
   wm::ActivateWindow(w1.get());
   ASSERT_EQ("1 M1 active=1", StateString());
 }
 
 }  // namespace internal
 }  // namespace ash