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

ash/wm/workspace/workspace_manager_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_manager.h"
 
 #include "ash/ash_switches.h"
 #include "ash/screen_ash.h"
 #include "ash/shell.h"
 #include "ash/shell_window_ids.h"
@@ skipping 53 matching lines @@
     return Shell::GetContainer(
         Shell::GetPrimaryRootWindow(),
         kShellWindowId_DefaultContainer);
   }
 
   const std::vector<Workspace*>& workspaces() const {
     return manager_->workspaces_;
   }
 
   gfx::Rect GetFullscreenBounds(aura::Window* window) {
-    return gfx::Screen::GetDisplayNearestWindow(window).bounds();
+    return Shell::GetScreen()->GetDisplayNearestWindow(window).bounds();
   }
 
   Workspace* active_workspace() {
     return manager_->active_workspace_;
   }
 
   Workspace* FindBy(aura::Window* window) const {
     return manager_->FindBy(window);
   }
 
@@ skipping 647 matching lines @@
   wm::ActivateWindow(w1.get());
   w1->SetProperty(aura::client::kShowStateKey, ui::SHOW_STATE_MAXIMIZED);
   w1->SetProperty(aura::client::kShowStateKey, ui::SHOW_STATE_MINIMIZED);
   EXPECT_EQ(ShelfLayoutManager::VISIBLE,
             Shell::GetInstance()->shelf()->visibility_state());
   EXPECT_FALSE(Shell::GetInstance()->launcher()->paints_background());
 }
 
 }  // namespace internal
 }  // namespace ash