Change UTF8ToUTF16 to accept const StringPiece&.

base/utf_string_conversions.h

 // Copyright (c) 2009 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_
 #pragma once
 
 #include <string>
 
 #include "base/string16.h"
-
-namespace base {
-class StringPiece;
-}
+#include "base/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.
 bool WideToUTF8(const wchar_t* src, size_t src_len, std::string* output);
 std::string WideToUTF8(const std::wstring& wide);
 bool UTF8ToWide(const char* src, size_t src_len, std::wstring* output);
 std::wstring UTF8ToWide(const base::StringPiece& utf8);
 
 bool WideToUTF16(const wchar_t* src, size_t src_len, string16* output);
 string16 WideToUTF16(const std::wstring& wide);
 bool UTF16ToWide(const char16* src, size_t src_len, std::wstring* output);
 std::wstring UTF16ToWide(const string16& utf16);
 
 bool UTF8ToUTF16(const char* src, size_t src_len, string16* output);
-string16 UTF8ToUTF16(const std::string& utf8);
+string16 UTF8ToUTF16(const base::StringPiece& utf8);
 bool UTF16ToUTF8(const char16* src, size_t src_len, std::string* output);
 std::string UTF16ToUTF8(const string16& utf16);
 
 // We are trying to get rid of wstring as much as possible, but it's too big
 // a mess to do it all at once.  These conversions should be used when we
 // really should just be passing a string16 around, but we haven't finished
 // porting whatever module uses wstring and the conversion is being used as a
 // stopcock.  This makes it easy to grep for the ones that should be removed.
 #if defined(OS_WIN)
 # define WideToUTF16Hack
 # define UTF16ToWideHack
 #else
 # define WideToUTF16Hack WideToUTF16
 # define UTF16ToWideHack UTF16ToWide
 #endif
 
 // These convert an ASCII string, typically a hardcoded constant, to a
 // UTF16/Wide string.
-//
-// Note that this doesn't use StringPiece because it's very common to need
-// ASCIIToUTF16("foo"), and either we have to include it in this file, or
-// forward declare it and force all callers to include string_piece.h. Given
-// that string_piece brings in complicated stuff like <algorithm>, it's
-// easier to just duplicate these very simple definitions for the two calling
-// cases we actually use.
-std::wstring ASCIIToWide(const char* ascii);
-std::wstring ASCIIToWide(const std::string& ascii);
-string16 ASCIIToUTF16(const char* ascii);
-string16 ASCIIToUTF16(const std::string& ascii);
+std::wstring ASCIIToWide(const base::StringPiece& ascii);
+string16 ASCIIToUTF16(const base::StringPiece& ascii);
 
 #endif  // BASE_UTF_STRING_CONVERSIONS_H_