Use a direct include of strings headers in ui/, part 1.

ui/base/clipboard/clipboard_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 "build/build_config.h"
 
 #include <string>
 
 #include "base/basictypes.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/message_loop.h"
 #include "base/pickle.h"
-#include "base/string_util.h"
+#include "base/strings/string_util.h"
 #include "base/strings/utf_string_conversions.h"
 #include "testing/gtest/include/gtest/gtest.h"
 #include "testing/platform_test.h"
 #include "third_party/skia/include/core/SkBitmap.h"
 #include "ui/base/clipboard/clipboard.h"
 #include "ui/base/clipboard/scoped_clipboard_writer.h"
 #include "ui/gfx/size.h"
 
 #if defined(OS_WIN)
 #include "ui/base/clipboard/clipboard_util_win.h"
@@ skipping 664 matching lines @@
   EXPECT_TRUE(clipboard().IsFormatAvailable(
       Clipboard::GetPlainTextWFormatType(), Clipboard::BUFFER_STANDARD));
 
   // Make sure the text is what we inserted while simulating the other app
   std::string contents;
   clipboard().ReadAsciiText(Clipboard::BUFFER_STANDARD, &contents);
   EXPECT_EQ(contents, new_value);
 }
 #endif
 }  // namespace ui