Adds a flag to support "Virtual Time" to the blink scheduler

components/scheduler/child/scheduler_task_runner_delegate_impl_unittest.cc

-// Copyright 2015 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 "components/scheduler/child/scheduler_task_runner_delegate_impl.h"
-
-#include "base/message_loop/message_loop.h"
-#include "base/test/test_simple_task_runner.h"
-#include "testing/gtest/include/gtest/gtest.h"
-
-namespace scheduler {
-
-TEST(SchedulerTaskRunnerDelegateImplTest, TestTaskRunnerOverriding) {
-  base::MessageLoop loop;
-  scoped_refptr<base::SingleThreadTaskRunner> original_runner(
-      loop.task_runner());
-  scoped_refptr<base::SingleThreadTaskRunner> custom_runner(
-      new base::TestSimpleTaskRunner());
-  {
-    scoped_refptr<SchedulerTaskRunnerDelegateImpl> delegate(
-        SchedulerTaskRunnerDelegateImpl::Create(&loop));
-    delegate->SetDefaultTaskRunner(custom_runner);
-    DCHECK_EQ(custom_runner, loop.task_runner());
-  }
-  DCHECK_EQ(original_runner, loop.task_runner());
-}
-
-}  // namespace scheduler