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

base/strings/sys_string_conversions.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 BASE_STRINGS_SYS_STRING_CONVERSIONS_H_
 #define BASE_STRINGS_SYS_STRING_CONVERSIONS_H_
 
 // Provides system-dependent string type conversions for cases where it's
 // necessary to not use ICU. Generally, you should not need this in Chrome,
 // but it is used in some shared code. Dependencies should be minimal.
 
 #include <string>
 
 #include "base/base_export.h"
 #include "base/basictypes.h"
 #include "base/string16.h"
-#include "base/string_piece.h"
+#include "base/strings/string_piece.h"
 
 #if defined(OS_MACOSX)
 #include <CoreFoundation/CoreFoundation.h>
 #ifdef __OBJC__
 @class NSString;
 #else
 class NSString;
 #endif
 #endif  // OS_MACOSX
 
@@ skipping 46 matching lines @@
 // Same, but accepts NSString input. Converts nil NSString* to the appropriate
 // string type of length 0.
 BASE_EXPORT std::string SysNSStringToUTF8(NSString* ref);
 BASE_EXPORT string16 SysNSStringToUTF16(NSString* ref);
 
 #endif  // defined(OS_MACOSX)
 
 }  // namespace base
 
 #endif  // BASE_STRINGS_SYS_STRING_CONVERSIONS_H_