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

ppapi/native_client/tests/ppapi_test_lib/testable_callback.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 "ppapi/c/dev/ppb_testing_dev.h"
 #include "ppapi/c/pp_errors.h"
 #include "native_client/tests/ppapi_test_lib/get_browser_interface.h"
 #include "native_client/tests/ppapi_test_lib/testable_callback.h"
 
 TestableCallback::TestableCallback(PP_Instance instance, bool force_async)
     : have_result_(false),
@@ skipping 32 matching lines @@
 void TestableCallback::Handler(void* user_data, int32_t result) {
   TestableCallback* callback = static_cast<TestableCallback*>(user_data);
   callback->result_ = result;
   callback->have_result_ = true;
   ++callback->run_count_;
   if (callback->post_quit_task_) {
     callback->post_quit_task_ = false;
     PPBTestingDev()->QuitMessageLoop(callback->instance_);
   }
 }