Use ScopedTaskEnvironment instead of MessageLoop in chrome unit tests.

chrome/browser/process_singleton_posix_unittest.cc

 // Copyright 2014 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 "chrome/browser/process_singleton.h"
 
 #include <fcntl.h>
 #include <limits.h>
 #include <signal.h>
 #include <stddef.h>
 #include <sys/types.h>
 #include <sys/un.h>
 #include <sys/wait.h>
 #include <unistd.h>
 
 #include <memory>
 #include <string>
 #include <vector>
 
 #include "base/bind.h"
 #include "base/command_line.h"
 #include "base/files/file_path.h"
 #include "base/files/file_util.h"
 #include "base/files/scoped_temp_dir.h"
 #include "base/location.h"
 #include "base/posix/eintr_wrapper.h"
 #include "base/single_thread_task_runner.h"
 #include "base/strings/stringprintf.h"
 #include "base/synchronization/waitable_event.h"
+#include "base/test/scoped_task_environment.h"
 #include "base/test/test_timeouts.h"
 #include "base/test/thread_test_helper.h"
 #include "base/threading/thread.h"
 #include "build/build_config.h"
 #include "chrome/common/chrome_constants.h"
 #include "content/public/test/test_browser_thread.h"
 #include "net/base/network_interfaces.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
 using content::BrowserThread;
@@ skipping 210 matching lines @@
 
   void DestructProcessSingleton() {
     ASSERT_TRUE(process_singleton_on_thread_);
     delete process_singleton_on_thread_;
   }
 
   void KillCallback(int pid) {
     kill_callbacks_++;
   }
 
-  base::MessageLoop message_loop_;
+  base::test::ScopedTaskEnvironment scoped_task_environment_;
   content::TestBrowserThread io_thread_;
   base::ScopedTempDir temp_dir_;
   base::WaitableEvent wait_event_;
   base::WaitableEvent signal_event_;
 
   std::unique_ptr<base::Thread> worker_thread_;
   TestableProcessSingleton* process_singleton_on_thread_;
 };
 
 }  // namespace
@@ skipping 156 matching lines @@
 // Test that if there is an existing lock file, and it's not locked, we replace
 // it.
 TEST_F(ProcessSingletonPosixTest, CreateReplacesOldMacLock) {
   std::unique_ptr<TestableProcessSingleton> process_singleton(
       CreateProcessSingleton());
   EXPECT_EQ(0, base::WriteFile(lock_path_, "", 0));
   EXPECT_TRUE(process_singleton->Create());
   VerifyFiles();
 }
 #endif  // defined(OS_MACOSX)