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

base/files/file_path.cc

 // 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/files/file_path.h"
 
 #include <string.h>
 #include <algorithm>
 
 #include "base/basictypes.h"
 #include "base/logging.h"
 #include "base/pickle.h"
 
 // These includes are just for the *Hack functions, and should be removed
 // when those functions are removed.
-#include "base/string_piece.h"
 #include "base/string_util.h"
+#include "base/strings/string_piece.h"
 #include "base/strings/sys_string_conversions.h"
 #include "base/utf_string_conversions.h"
 
 #if defined(OS_MACOSX)
 #include "base/mac/scoped_cftyperef.h"
 #include "base/third_party/icu/icu_utf.h"
 #endif
 
 #if defined(OS_WIN)
 #include <windows.h>
@@ skipping 1223 matching lines @@
 #else
   return *this;
 #endif
 }
 
 }  // namespace base
 
 void PrintTo(const base::FilePath& path, std::ostream* out) {
   *out << path.value();
 }