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

components/scheduler/renderer/idle_time_estimator.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/idle_time_estimator.h"
 
 #include "base/time/default_tick_clock.h"
 
 namespace scheduler {
 
 IdleTimeEstimator::IdleTimeEstimator(
     const scoped_refptr<TaskQueue>& compositor_task_runner,
+    base::TickClock* time_source,
     int sample_count,
     double estimation_percentile)
     : compositor_task_runner_(compositor_task_runner),
       per_frame_compositor_task_runtime_(sample_count),
-      time_source_(new base::DefaultTickClock),
+      time_source_(time_source),
       estimation_percentile_(estimation_percentile),
       nesting_level_(0),
       did_commit_(false) {
   compositor_task_runner_->AddTaskObserver(this);
 }
 
 IdleTimeEstimator::~IdleTimeEstimator() {
   compositor_task_runner_->RemoveTaskObserver(this);
 }
 
@@ skipping 13 matching lines @@
 }
 
 void IdleTimeEstimator::Clear() {
   task_start_time_ = base::TimeTicks();
   prev_commit_time_ = base::TimeTicks();
   cumulative_compositor_runtime_ = base::TimeDelta();
   per_frame_compositor_task_runtime_.Clear();
   did_commit_ = false;
 }
 
-void IdleTimeEstimator::SetTimeSourceForTesting(
-    scoped_ptr<base::TickClock> time_source) {
-  time_source_ = time_source.Pass();
-}
-
 void IdleTimeEstimator::WillProcessTask(const base::PendingTask& pending_task) {
   nesting_level_++;
   if (nesting_level_ == 1)
     task_start_time_ = time_source_->NowTicks();
 }
 
 void IdleTimeEstimator::DidProcessTask(const base::PendingTask& pending_task) {
   nesting_level_--;
   DCHECK_GE(nesting_level_, 0);
   if (nesting_level_ != 0)
     return;
 
   cumulative_compositor_runtime_ += time_source_->NowTicks() - task_start_time_;
 
   if (did_commit_) {
     per_frame_compositor_task_runtime_.InsertSample(
         cumulative_compositor_runtime_);
     cumulative_compositor_runtime_ = base::TimeDelta();
     did_commit_ = false;
   }
 }
 
 }  // namespace scheduler