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

dbus/object_proxy.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 "dbus/bus.h"
 
 #include "base/bind.h"
 #include "base/logging.h"
 #include "base/message_loop.h"
 #include "base/metrics/histogram.h"
-#include "base/string_piece.h"
 #include "base/stringprintf.h"
+#include "base/strings/string_piece.h"
 #include "base/threading/thread.h"
 #include "base/threading/thread_restrictions.h"
 #include "dbus/dbus_statistics.h"
 #include "dbus/message.h"
 #include "dbus/object_path.h"
 #include "dbus/object_proxy.h"
 #include "dbus/scoped_dbus_error.h"
 
 namespace {
 
@@ skipping 640 matching lines @@
       }
     }
   }
 
   // Always return unhandled to let other object proxies handle the same
   // signal.
   return DBUS_HANDLER_RESULT_NOT_YET_HANDLED;
 }
 
 }  // namespace dbus