Use a direct include of strings headers in ui/, part 3.

ui/gfx/font_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 "ui/gfx/font.h"
 
-#include "base/string16.h"
+#include "base/strings/string16.h"
 #include "base/strings/utf_string_conversions.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
 #if defined(OS_POSIX) && !defined(OS_MACOSX) && !defined(OS_ANDROID)
 #include <pango/pango.h>
 #elif defined(OS_WIN)
 #include "ui/gfx/platform_font_win.h"
 #endif
 
 namespace gfx {
@@ skipping 109 matching lines @@
   // The minimum font size is set to 5 in browser_main.cc.
   ScopedMinimumFontSizeCallback minimum_size(5);
 
   Font derived_font = cf.DeriveFont(-2);
   EXPECT_EQ(6, derived_font.GetFontSize());
 }
 #endif  // defined(OS_WIN)
 
 }  // namespace
 }  // namespace gfx