Update Native Client Authors to be Chromium Authors for the code moved from the

ppapi/native_client/src/shared/ppapi_proxy/plugin_resource_tracker.cc

-// Copyright (c) 2011 The Native Client Authors. All rights reserved.
+// Copyright (c) 2011 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 "native_client/src/shared/ppapi_proxy/plugin_resource_tracker.h"
 
 #include <limits>
 #include <set>
 
 #include "native_client/src/include/nacl_macros.h"
 #include "native_client/src/include/portability.h"
@@ skipping 80 matching lines @@
   // Release all browser references.
   if (res && (browser_refcount > 0)) {
     NaClSrpcChannel* channel = ppapi_proxy::GetMainSrpcChannel();
     PpbCoreRpcClient::ReleaseResourceMultipleTimes(channel, res,
                                                    browser_refcount);
   }
 }
 
 }  // namespace ppapi_proxy