[Reland] Per WebViewScheduler virtual time

components/scheduler/renderer/web_view_scheduler_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/renderer/web_view_scheduler_impl.h"
 
 #include "base/callback.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/test/simple_test_tick_clock.h"
 #include "cc/test/ordered_simple_task_runner.h"
@@ skipping 249 matching lines @@
   web_view_scheduler_->setPageVisible(false);
   base::TimeTicks initial_real_time = scheduler_->tick_clock()->NowTicks();
 
   int run_count = 0;
   web_frame_scheduler_->timerTaskRunner()->postDelayedTask(
       BLINK_FROM_HERE,
       new RepeatingTask(web_frame_scheduler_->timerTaskRunner(), &run_count),
       1.0);
 
   mock_task_runner_->RunTasksWhile(mock_task_runner_->TaskRunCountBelow(2000));
+  // Virtual time means page visibility is ignored.
   EXPECT_EQ(1999, run_count);
 
   // The global tick clock has not moved, yet we ran a large number of "delayed"
   // tasks despite calling setPageVisible(false).
   EXPECT_EQ(initial_real_time, scheduler_->tick_clock()->NowTicks());
 }
 
 namespace {
 class RunOrderTask : public blink::WebTaskRunner::Task {
  public:
@@ skipping 175 matching lines @@
   // it will prevent further tasks from running (i.e. the RepeatingTask) by
   // deleting the WebFrameScheduler.
   timer_task_runner->postDelayedTask(BLINK_FROM_HERE, delete_frame_task,
                                      9990.0);
 
   mock_task_runner_->RunForPeriod(base::TimeDelta::FromSeconds(100));
   EXPECT_EQ(10, run_count);
 }
 
 }  // namespace scheduler