base: Update the include paths of base/string_piece.h to its new location.

base/utf_string_conversions.h

 // Copyright (c) 2011 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 BASE_UTF_STRING_CONVERSIONS_H_
 #define BASE_UTF_STRING_CONVERSIONS_H_
 
 #include <string>
 
 #include "base/base_export.h"
 #include "base/string16.h"
-#include "base/string_piece.h"
+#include "base/strings/string_piece.h"
 
 // These convert between UTF-8, -16, and -32 strings. They are potentially slow,
 // so avoid unnecessary conversions. The low-level versions return a boolean
 // indicating whether the conversion was 100% valid. In this case, it will still
 // do the best it can and put the result in the output buffer. The versions that
 // return strings ignore this error and just return the best conversion
 // possible.
 BASE_EXPORT bool WideToUTF8(const wchar_t* src, size_t src_len,
                             std::string* output);
 BASE_EXPORT std::string WideToUTF8(const std::wstring& wide);
@@ skipping 26 matching lines @@
 # define WideToUTF16Hack WideToUTF16
 # define UTF16ToWideHack UTF16ToWide
 #endif
 
 // These convert an ASCII string, typically a hardcoded constant, to a
 // UTF16/Wide string.
 BASE_EXPORT std::wstring ASCIIToWide(const base::StringPiece& ascii);
 BASE_EXPORT string16 ASCIIToUTF16(const base::StringPiece& ascii);
 
 #endif  // BASE_UTF_STRING_CONVERSIONS_H_