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

base/strings/sys_string_conversions_mac.mm

 // 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 "base/strings/sys_string_conversions.h"
 
 #import <Foundation/Foundation.h>
 
 #include <vector>
 
 #include "base/mac/foundation_util.h"
 #include "base/mac/scoped_cftyperef.h"
-#include "base/string_piece.h"
+#include "base/strings/string_piece.h"
 
 namespace base {
 
 namespace {
 
 // Convert the supplied CFString into the specified encoding, and return it as
 // an STL string of the template type.  Returns an empty string on failure.
 //
 // Do not assert in this function since it is used by the asssertion code!
 template<typename StringType>
@@ skipping 154 matching lines @@
   return SysCFStringRefToUTF8(reinterpret_cast<CFStringRef>(nsstring));
 }
 
 string16 SysNSStringToUTF16(NSString* nsstring) {
   if (!nsstring)
     return string16();
   return SysCFStringRefToUTF16(reinterpret_cast<CFStringRef>(nsstring));
 }
 
 }  // namespace base