Move more uses of string16 to specify base::

ui/gfx/utf16_indexing.h

 // 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.
 
 #ifndef UI_GFX_UTF16_INDEXING_H_
 #define UI_GFX_UTF16_INDEXING_H_
 
 #include "base/strings/string16.h"
 #include "ui/gfx/gfx_export.h"
 
 namespace gfx {
 
 // Returns false if s[index-1] is a high surrogate and s[index] is a low
 // surrogate, true otherwise.
-GFX_EXPORT bool IsValidCodePointIndex(const string16& s, size_t index);
+GFX_EXPORT bool IsValidCodePointIndex(const base::string16& s, size_t index);
 
 // |UTF16IndexToOffset| returns the number of code points between |base| and
 // |pos| in the given string. |UTF16OffsetToIndex| returns the index that is
 // |offset| code points away from the given |base| index. These functions are
 // named after glib's |g_utf8_pointer_to_offset| and |g_utf8_offset_to_pointer|,
 // which perform the same function for UTF-8. As in glib, it is an error to
 // pass an |offset| that walks off the edge of the string.
 //
 // These functions attempt to deal with invalid use of UTF-16 surrogates in a
 // way that makes as much sense as possible: unpaired surrogates are treated as
 // single characters, and if an argument index points to the middle of a valid
 // surrogate pair, it is treated as though it pointed to the end of that pair.
 // The index returned by |UTF16OffsetToIndex| never points to the middle of a
 // surrogate pair.
 //
 // The following identities hold:
 //   If |s| contains no surrogate pairs, then
 //     UTF16IndexToOffset(s, base, pos) == pos - base
 //     UTF16OffsetToIndex(s, base, offset) == base + offset
 //   If |pos| does not point to the middle of a surrogate pair, then
 //     UTF16OffsetToIndex(s, base, UTF16IndexToOffset(s, base, pos)) == pos
 //   Always,
 //     UTF16IndexToOffset(s, base, UTF16OffsetToIndex(s, base, ofs)) == ofs
 //     UTF16IndexToOffset(s, i, j) == -UTF16IndexToOffset(s, j, i)
-GFX_EXPORT ptrdiff_t UTF16IndexToOffset(const string16& s,
+GFX_EXPORT ptrdiff_t UTF16IndexToOffset(const base::string16& s,
                                         size_t base,
                                         size_t pos);
-GFX_EXPORT size_t UTF16OffsetToIndex(const string16& s,
+GFX_EXPORT size_t UTF16OffsetToIndex(const base::string16& s,
                                      size_t base,
                                      ptrdiff_t offset);
 
 }  // namespace gfx
 
 #endif  // UI_GFX_UTF16_INDEXING_H_