[Cleanup] Remove StringPrintf from global namespace

ash/display/display_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/display/display_manager.h"
 
 #include "ash/display/display_controller.h"
 #include "ash/screen_ash.h"
 #include "ash/shell.h"
 #include "ash/test/ash_test_base.h"
 #include "ash/test/display_manager_test_api.h"
 #include "base/format_macros.h"
 #include "base/stringprintf.h"
 #include "ui/aura/env.h"
 #include "ui/aura/root_window.h"
 #include "ui/aura/window_observer.h"
 #include "ui/gfx/display_observer.h"
 #include "ui/gfx/display.h"
 
 namespace ash {
 namespace internal {
 
 using std::vector;
 using std::string;
 
+using base::StringPrintf;
+
 class DisplayManagerTest : public test::AshTestBase,
                            public gfx::DisplayObserver,
                            public aura::WindowObserver {
  public:
   DisplayManagerTest()
       : removed_count_(0U),
         root_window_destroyed_(false) {
   }
   virtual ~DisplayManagerTest() {}
 
@@ skipping 642 matching lines @@
             GetDisplayInfoAt(0).size_in_pixel().ToString());
 
   EXPECT_EQ("1,201 300x400",
             GetDisplayInfoAt(1).bounds_in_pixel().ToString());
   EXPECT_EQ("300x400",
             GetDisplayInfoAt(1).size_in_pixel().ToString());
 }
 
 }  // namespace internal
 }  // namespace ash