Introduce a SchedulerHelper in content/child/scheduler

content/child/scheduler/scheduler_helper.cc

Index: content/child/scheduler/scheduler_helper.cc
diff --git a/content/renderer/scheduler/renderer_scheduler_impl.cc b/content/child/scheduler/scheduler_helper.cc
similarity index 22%
copy from content/renderer/scheduler/renderer_scheduler_impl.cc
copy to content/child/scheduler/scheduler_helper.cc
index 53281b81a807a7389d7e3917b86ef822d5c3bcc4..cc03d22d4740423d3932ae40718e3b5c48623f93 100644
--- a/content/renderer/scheduler/renderer_scheduler_impl.cc
+++ b/content/child/scheduler/scheduler_helper.cc
@@ -1,431 +1,119 @@
-// Copyright 2014 The Chromium Authors. All rights reserved.
+// 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 "content/renderer/scheduler/renderer_scheduler_impl.h"
+#include "content/child/scheduler/scheduler_helper.h"
 
-#include "base/bind.h"
-#include "base/message_loop/message_loop_proxy.h"
 #include "base/trace_event/trace_event.h"
 #include "base/trace_event/trace_event_argument.h"
-#include "cc/output/begin_frame_args.h"
-#include "content/renderer/scheduler/nestable_single_thread_task_runner.h"
-#include "content/renderer/scheduler/renderer_task_queue_selector.h"
-#include "ui/gfx/frame_time.h"
+#include "content/child/scheduler/nestable_single_thread_task_runner.h"
+#include "content/child/scheduler/prioritizing_task_queue_selector.h"
 
 namespace content {
 
-RendererSchedulerImpl::RendererSchedulerImpl(
-    scoped_refptr<NestableSingleThreadTaskRunner> main_task_runner)
-    : renderer_task_queue_selector_(new RendererTaskQueueSelector()),
+SchedulerHelper::SchedulerHelper(
+    scoped_refptr<NestableSingleThreadTaskRunner> main_task_runner,
+    SchedulerHelperDelegate* scheduler_helper_delegate,
+    const char* tracing_category,
+    const char* disabled_by_default_tracing_category,
+    size_t total_task_queue_count)
+    : task_queue_selector_(new PrioritizingTaskQueueSelector()),
       task_queue_manager_(
-          new TaskQueueManager(TASK_QUEUE_COUNT,
+          new TaskQueueManager(total_task_queue_count,
                                main_task_runner,
-                               renderer_task_queue_selector_.get())),
+                               task_queue_selector_.get(),
+                               disabled_by_default_tracing_category)),
+      idle_period_state_(IdlePeriodState::NOT_IN_IDLE_PERIOD),
+      scheduler_helper_delegate_(scheduler_helper_delegate),
       control_task_runner_(
-          task_queue_manager_->TaskRunnerForQueue(CONTROL_TASK_QUEUE)),
+          task_queue_manager_->TaskRunnerForQueue(QueueId::CONTROL_TASK_QUEUE)),
       control_task_after_wakeup_runner_(task_queue_manager_->TaskRunnerForQueue(
-          CONTROL_TASK_AFTER_WAKEUP_QUEUE)),
+          QueueId::CONTROL_TASK_AFTER_WAKEUP_QUEUE)),
       default_task_runner_(
-          task_queue_manager_->TaskRunnerForQueue(DEFAULT_TASK_QUEUE)),
-      compositor_task_runner_(
-          task_queue_manager_->TaskRunnerForQueue(COMPOSITOR_TASK_QUEUE)),
-      loading_task_runner_(
-          task_queue_manager_->TaskRunnerForQueue(LOADING_TASK_QUEUE)),
-      delayed_update_policy_runner_(
-          base::Bind(&RendererSchedulerImpl::UpdatePolicy,
-                     base::Unretained(this)),
-          control_task_runner_),
-      current_policy_(Policy::NORMAL),
-      idle_period_state_(IdlePeriodState::NOT_IN_IDLE_PERIOD),
-      last_input_type_(blink::WebInputEvent::Undefined),
-      input_stream_state_(InputStreamState::INACTIVE),
-      policy_may_need_update_(&incoming_signals_lock_),
+          task_queue_manager_->TaskRunnerForQueue(QueueId::DEFAULT_TASK_QUEUE)),
+      tracing_category_(tracing_category),
+      disabled_by_default_tracing_category_(
+          disabled_by_default_tracing_category),
       weak_factory_(this) {
-  weak_renderer_scheduler_ptr_ = weak_factory_.GetWeakPtr();
-  update_policy_closure_ = base::Bind(&RendererSchedulerImpl::UpdatePolicy,
-                                      weak_renderer_scheduler_ptr_);
-  end_idle_period_closure_.Reset(base::Bind(
-      &RendererSchedulerImpl::EndIdlePeriod, weak_renderer_scheduler_ptr_));
+  DCHECK_GE(total_task_queue_count, QueueId::TASK_QUEUE_COUNT);
+  weak_scheduler_ptr_ = weak_factory_.GetWeakPtr();
+  end_idle_period_closure_.Reset(
+      base::Bind(&SchedulerHelper::EndIdlePeriod, weak_scheduler_ptr_));
   initiate_next_long_idle_period_closure_.Reset(base::Bind(
-      &RendererSchedulerImpl::InitiateLongIdlePeriod,
-      weak_renderer_scheduler_ptr_));
-  initiate_next_long_idle_period_after_wakeup_closure_.Reset(base::Bind(
-      &RendererSchedulerImpl::InitiateLongIdlePeriodAfterWakeup,
-      weak_renderer_scheduler_ptr_));
+      &SchedulerHelper::InitiateLongIdlePeriod, weak_scheduler_ptr_));
+  initiate_next_long_idle_period_after_wakeup_closure_.Reset(
+      base::Bind(&SchedulerHelper::InitiateLongIdlePeriodAfterWakeup,
+                 weak_scheduler_ptr_));
 
   idle_task_runner_ = make_scoped_refptr(new SingleThreadIdleTaskRunner(
-      task_queue_manager_->TaskRunnerForQueue(IDLE_TASK_QUEUE),
+      task_queue_manager_->TaskRunnerForQueue(QueueId::IDLE_TASK_QUEUE),
       control_task_after_wakeup_runner_,
-      base::Bind(&RendererSchedulerImpl::CurrentIdleTaskDeadlineCallback,
-                 weak_renderer_scheduler_ptr_)));
+      base::Bind(&SchedulerHelper::CurrentIdleTaskDeadlineCallback,
+                 weak_scheduler_ptr_),
+      tracing_category));
 
-  renderer_task_queue_selector_->SetQueuePriority(
-      CONTROL_TASK_QUEUE, RendererTaskQueueSelector::CONTROL_PRIORITY);
+  task_queue_selector_->SetQueuePriority(
+      QueueId::CONTROL_TASK_QUEUE,
+      PrioritizingTaskQueueSelector::CONTROL_PRIORITY);
 
-  renderer_task_queue_selector_->SetQueuePriority(
-      CONTROL_TASK_AFTER_WAKEUP_QUEUE,
-      RendererTaskQueueSelector::CONTROL_PRIORITY);
+  task_queue_selector_->SetQueuePriority(
+      QueueId::CONTROL_TASK_AFTER_WAKEUP_QUEUE,
+      PrioritizingTaskQueueSelector::CONTROL_PRIORITY);
   task_queue_manager_->SetPumpPolicy(
-      CONTROL_TASK_AFTER_WAKEUP_QUEUE,
+      QueueId::CONTROL_TASK_AFTER_WAKEUP_QUEUE,
       TaskQueueManager::PumpPolicy::AFTER_WAKEUP);
 
-  renderer_task_queue_selector_->DisableQueue(IDLE_TASK_QUEUE);
-  task_queue_manager_->SetPumpPolicy(IDLE_TASK_QUEUE,
+  task_queue_selector_->DisableQueue(QueueId::IDLE_TASK_QUEUE);
+  task_queue_manager_->SetPumpPolicy(QueueId::IDLE_TASK_QUEUE,
                                      TaskQueueManager::PumpPolicy::MANUAL);
 
   // TODO(skyostil): Increase this to 4 (crbug.com/444764).
   task_queue_manager_->SetWorkBatchSize(1);
+}
 
-  for (size_t i = 0; i < TASK_QUEUE_COUNT; i++) {
-    task_queue_manager_->SetQueueName(
-        i, TaskQueueIdToString(static_cast<QueueId>(i)));
-  }
-  TRACE_EVENT_OBJECT_CREATED_WITH_ID(
-      TRACE_DISABLED_BY_DEFAULT("renderer.scheduler"), "RendererScheduler",
-      this);
+SchedulerHelper::~SchedulerHelper() {
 }
 
-RendererSchedulerImpl::~RendererSchedulerImpl() {
-  TRACE_EVENT_OBJECT_DELETED_WITH_ID(
-      TRACE_DISABLED_BY_DEFAULT("renderer.scheduler"), "RendererScheduler",
-      this);
+SchedulerHelper::SchedulerHelperDelegate::SchedulerHelperDelegate() {
 }
 
-void RendererSchedulerImpl::Shutdown() {
-  DCHECK(main_thread_checker_.CalledOnValidThread());
-  task_queue_manager_.reset();
+SchedulerHelper::SchedulerHelperDelegate::~SchedulerHelperDelegate() {
 }
 
-scoped_refptr<base::SingleThreadTaskRunner>
-RendererSchedulerImpl::DefaultTaskRunner() {
-  DCHECK(main_thread_checker_.CalledOnValidThread());
-  return default_task_runner_;
+void SchedulerHelper::Shutdown() {
+  CheckOnValidThread();
+  task_queue_manager_.reset();
 }
 
 scoped_refptr<base::SingleThreadTaskRunner>
-RendererSchedulerImpl::CompositorTaskRunner() {
-  DCHECK(main_thread_checker_.CalledOnValidThread());
-  return compositor_task_runner_;
+SchedulerHelper::DefaultTaskRunner() {
+  CheckOnValidThread();
+  return default_task_runner_;
 }
 
-scoped_refptr<SingleThreadIdleTaskRunner>
-RendererSchedulerImpl::IdleTaskRunner() {
-  DCHECK(main_thread_checker_.CalledOnValidThread());
+scoped_refptr<SingleThreadIdleTaskRunner> SchedulerHelper::IdleTaskRunner() {
+  CheckOnValidThread();
   return idle_task_runner_;
 }
 
 scoped_refptr<base::SingleThreadTaskRunner>
-RendererSchedulerImpl::LoadingTaskRunner() {
-  DCHECK(main_thread_checker_.CalledOnValidThread());
-  return loading_task_runner_;
-}
-
-void RendererSchedulerImpl::WillBeginFrame(const cc::BeginFrameArgs& args) {
-  TRACE_EVENT1(TRACE_DISABLED_BY_DEFAULT("renderer.scheduler"),
-               "RendererSchedulerImpl::WillBeginFrame", "args", args.AsValue());
-  DCHECK(main_thread_checker_.CalledOnValidThread());
-  if (!task_queue_manager_)
-    return;
-
-  EndIdlePeriod();
-  estimated_next_frame_begin_ = args.frame_time + args.interval;
-  // TODO(skyostil): Wire up real notification of input events processing
-  // instead of this approximation.
-  DidProcessInputEvent(args.frame_time);
+SchedulerHelper::ControlTaskRunner() {
+  return control_task_runner_;
 }
 
-void RendererSchedulerImpl::DidCommitFrameToCompositor() {
-  TRACE_EVENT0(TRACE_DISABLED_BY_DEFAULT("renderer.scheduler"),
-               "RendererSchedulerImpl::DidCommitFrameToCompositor");
-  DCHECK(main_thread_checker_.CalledOnValidThread());
-  if (!task_queue_manager_)
-    return;
-
-  base::TimeTicks now(Now());
-  if (now < estimated_next_frame_begin_) {
-    // TODO(rmcilroy): Consider reducing the idle period based on the runtime of
-    // the next pending delayed tasks (as currently done in for long idle times)
-    StartIdlePeriod(IdlePeriodState::IN_SHORT_IDLE_PERIOD);
-    control_task_runner_->PostDelayedTask(FROM_HERE,
-                                          end_idle_period_closure_.callback(),
-                                          estimated_next_frame_begin_ - now);
-  }
-}
-
-void RendererSchedulerImpl::BeginFrameNotExpectedSoon() {
-  TRACE_EVENT0(TRACE_DISABLED_BY_DEFAULT("renderer.scheduler"),
-               "RendererSchedulerImpl::BeginFrameNotExpectedSoon");
-  DCHECK(main_thread_checker_.CalledOnValidThread());
-  if (!task_queue_manager_)
-    return;
-
-  // TODO(skyostil): Wire up real notification of input events processing
-  // instead of this approximation.
-  DidProcessInputEvent(base::TimeTicks());
-
-  InitiateLongIdlePeriod();
-}
-
-void RendererSchedulerImpl::DidReceiveInputEventOnCompositorThread(
-    const blink::WebInputEvent& web_input_event) {
-  TRACE_EVENT0(TRACE_DISABLED_BY_DEFAULT("renderer.scheduler"),
-               "RendererSchedulerImpl::DidReceiveInputEventOnCompositorThread");
-  // We regard MouseMove events with the left mouse button down as a signal
-  // that the user is doing something requiring a smooth frame rate.
-  if (web_input_event.type == blink::WebInputEvent::MouseMove &&
-      (web_input_event.modifiers & blink::WebInputEvent::LeftButtonDown)) {
-    UpdateForInputEvent(web_input_event.type);
-    return;
-  }
-  // Ignore all other mouse events because they probably don't signal user
-  // interaction needing a smooth framerate. NOTE isMouseEventType returns false
-  // for mouse wheel events, hence we regard them as user input.
-  // Ignore keyboard events because it doesn't really make sense to enter
-  // compositor priority for them.
-  if (blink::WebInputEvent::isMouseEventType(web_input_event.type) ||
-      blink::WebInputEvent::isKeyboardEventType(web_input_event.type)) {
-    return;
-  }
-  UpdateForInputEvent(web_input_event.type);
-}
-
-void RendererSchedulerImpl::DidAnimateForInputOnCompositorThread() {
-  UpdateForInputEvent(blink::WebInputEvent::Undefined);
-}
-
-void RendererSchedulerImpl::UpdateForInputEvent(
-    blink::WebInputEvent::Type type) {
-  base::AutoLock lock(incoming_signals_lock_);
-
-  InputStreamState new_input_stream_state =
-      ComputeNewInputStreamState(input_stream_state_, type, last_input_type_);
-
-  if (input_stream_state_ != new_input_stream_state) {
-    // Update scheduler policy if we should start a new policy mode.
-    input_stream_state_ = new_input_stream_state;
-    EnsureUrgentPolicyUpdatePostedOnMainThread(FROM_HERE);
-  }
-  last_input_receipt_time_on_compositor_ = Now();
-  // Clear the last known input processing time so that we know an input event
-  // is still queued up. This timestamp will be updated the next time the
-  // compositor commits or becomes quiescent. Note that this function is always
-  // called before the input event is processed either on the compositor or
-  // main threads.
-  last_input_process_time_on_main_ = base::TimeTicks();
-  last_input_type_ = type;
-}
-
-void RendererSchedulerImpl::DidProcessInputEvent(
-    base::TimeTicks begin_frame_time) {
-  DCHECK(main_thread_checker_.CalledOnValidThread());
-  base::AutoLock lock(incoming_signals_lock_);
-  if (input_stream_state_ == InputStreamState::INACTIVE)
-    return;
-  // Avoid marking input that arrived after the BeginFrame as processed.
-  if (!begin_frame_time.is_null() &&
-      begin_frame_time < last_input_receipt_time_on_compositor_)
-    return;
-  last_input_process_time_on_main_ = Now();
-  UpdatePolicyLocked();
-}
-
-bool RendererSchedulerImpl::IsHighPriorityWorkAnticipated() {
-  DCHECK(main_thread_checker_.CalledOnValidThread());
-  if (!task_queue_manager_)
-    return false;
-
-  MaybeUpdatePolicy();
-  // The touchstart and compositor policies indicate a strong likelihood of
-  // high-priority work in the near future.
-  return SchedulerPolicy() == Policy::COMPOSITOR_PRIORITY ||
-         SchedulerPolicy() == Policy::TOUCHSTART_PRIORITY;
-}
-
-bool RendererSchedulerImpl::ShouldYieldForHighPriorityWork() {
-  DCHECK(main_thread_checker_.CalledOnValidThread());
-  if (!task_queue_manager_)
-    return false;
-
-  MaybeUpdatePolicy();
-  // We only yield if we are in the compositor priority and there is compositor
-  // work outstanding, or if we are in the touchstart response priority.
-  // Note: even though the control queue is higher priority we don't yield for
-  // it since these tasks are not user-provided work and they are only intended
-  // to run before the next task, not interrupt the tasks.
-  switch (SchedulerPolicy()) {
-    case Policy::NORMAL:
-      return false;
-
-    case Policy::COMPOSITOR_PRIORITY:
-      return !task_queue_manager_->IsQueueEmpty(COMPOSITOR_TASK_QUEUE);
-
-    case Policy::TOUCHSTART_PRIORITY:
-      return true;
-
-    default:
-      NOTREACHED();
-      return false;
-  }
-}
-
-void RendererSchedulerImpl::CurrentIdleTaskDeadlineCallback(
+void SchedulerHelper::CurrentIdleTaskDeadlineCallback(
     base::TimeTicks* deadline_out) const {
-  DCHECK(main_thread_checker_.CalledOnValidThread());
-  *deadline_out = estimated_next_frame_begin_;
+  CheckOnValidThread();
+  *deadline_out = estimated_end_of_idle_;
 }
 
-RendererSchedulerImpl::Policy RendererSchedulerImpl::SchedulerPolicy() const {
-  DCHECK(main_thread_checker_.CalledOnValidThread());
-  return current_policy_;
-}
-
-void RendererSchedulerImpl::MaybeUpdatePolicy() {
-  DCHECK(main_thread_checker_.CalledOnValidThread());
-  if (policy_may_need_update_.IsSet()) {
-    UpdatePolicy();
-  }
-}
-
-void RendererSchedulerImpl::EnsureUrgentPolicyUpdatePostedOnMainThread(
-    const tracked_objects::Location& from_here) {
-  // TODO(scheduler-dev): Check that this method isn't called from the main
-  // thread.
-  incoming_signals_lock_.AssertAcquired();
-  if (!policy_may_need_update_.IsSet()) {
-    policy_may_need_update_.SetWhileLocked(true);
-    control_task_runner_->PostTask(from_here, update_policy_closure_);
-  }
-}
-
-void RendererSchedulerImpl::UpdatePolicy() {
-  base::AutoLock lock(incoming_signals_lock_);
-  UpdatePolicyLocked();
-}
-
-void RendererSchedulerImpl::UpdatePolicyLocked() {
-  DCHECK(main_thread_checker_.CalledOnValidThread());
-  incoming_signals_lock_.AssertAcquired();
-  if (!task_queue_manager_)
-    return;
-
-  base::TimeTicks now = Now();
-  policy_may_need_update_.SetWhileLocked(false);
-
-  base::TimeDelta new_policy_duration;
-  Policy new_policy = ComputeNewPolicy(now, &new_policy_duration);
-  if (new_policy_duration > base::TimeDelta()) {
-    current_policy_expiration_time_ = now + new_policy_duration;
-    delayed_update_policy_runner_.SetDeadline(FROM_HERE, new_policy_duration,
-                                              now);
-  } else {
-    current_policy_expiration_time_ = base::TimeTicks();
-  }
-
-  if (new_policy == current_policy_)
-    return;
-
-  switch (new_policy) {
-    case Policy::COMPOSITOR_PRIORITY:
-      renderer_task_queue_selector_->SetQueuePriority(
-          COMPOSITOR_TASK_QUEUE, RendererTaskQueueSelector::HIGH_PRIORITY);
-      // TODO(scheduler-dev): Add a task priority between HIGH and BEST_EFFORT
-      // that still has some guarantee of running.
-      renderer_task_queue_selector_->SetQueuePriority(
-          LOADING_TASK_QUEUE, RendererTaskQueueSelector::BEST_EFFORT_PRIORITY);
-      break;
-    case Policy::TOUCHSTART_PRIORITY:
-      renderer_task_queue_selector_->SetQueuePriority(
-          COMPOSITOR_TASK_QUEUE, RendererTaskQueueSelector::HIGH_PRIORITY);
-      renderer_task_queue_selector_->DisableQueue(LOADING_TASK_QUEUE);
-      break;
-    case Policy::NORMAL:
-      renderer_task_queue_selector_->SetQueuePriority(
-          COMPOSITOR_TASK_QUEUE, RendererTaskQueueSelector::NORMAL_PRIORITY);
-      renderer_task_queue_selector_->SetQueuePriority(
-          LOADING_TASK_QUEUE, RendererTaskQueueSelector::NORMAL_PRIORITY);
-      break;
-  }
-  DCHECK(renderer_task_queue_selector_->IsQueueEnabled(COMPOSITOR_TASK_QUEUE));
-  if (new_policy != Policy::TOUCHSTART_PRIORITY)
-    DCHECK(renderer_task_queue_selector_->IsQueueEnabled(LOADING_TASK_QUEUE));
-
-  current_policy_ = new_policy;
-
-  TRACE_EVENT_OBJECT_SNAPSHOT_WITH_ID(
-      TRACE_DISABLED_BY_DEFAULT("renderer.scheduler"), "RendererScheduler",
-      this, AsValueLocked(now));
-  TRACE_COUNTER1(TRACE_DISABLED_BY_DEFAULT("renderer.scheduler"),
-                 "RendererScheduler.policy", current_policy_);
-}
-
-RendererSchedulerImpl::Policy RendererSchedulerImpl::ComputeNewPolicy(
-    base::TimeTicks now,
-    base::TimeDelta* new_policy_duration) {
-  DCHECK(main_thread_checker_.CalledOnValidThread());
-  incoming_signals_lock_.AssertAcquired();
-
-  Policy new_policy = Policy::NORMAL;
-  *new_policy_duration = base::TimeDelta();
-
-  if (input_stream_state_ == InputStreamState::INACTIVE)
-    return new_policy;
-
-  Policy input_priority_policy =
-      input_stream_state_ ==
-              InputStreamState::ACTIVE_AND_AWAITING_TOUCHSTART_RESPONSE
-          ? Policy::TOUCHSTART_PRIORITY
-          : Policy::COMPOSITOR_PRIORITY;
-  base::TimeDelta time_left_in_policy = TimeLeftInInputEscalatedPolicy(now);
-  if (time_left_in_policy > base::TimeDelta()) {
-    new_policy = input_priority_policy;
-    *new_policy_duration = time_left_in_policy;
-  } else {
-    // Reset |input_stream_state_| to ensure
-    // DidReceiveInputEventOnCompositorThread will post an UpdatePolicy task
-    // when it's next called.
-    input_stream_state_ = InputStreamState::INACTIVE;
-  }
-  return new_policy;
-}
-
-base::TimeDelta RendererSchedulerImpl::TimeLeftInInputEscalatedPolicy(
-    base::TimeTicks now) const {
-  DCHECK(main_thread_checker_.CalledOnValidThread());
-  // TODO(rmcilroy): Change this to DCHECK_EQ when crbug.com/463869 is fixed.
-  DCHECK(input_stream_state_ != InputStreamState::INACTIVE);
-  incoming_signals_lock_.AssertAcquired();
-
-  base::TimeDelta escalated_priority_duration =
-      base::TimeDelta::FromMilliseconds(kPriorityEscalationAfterInputMillis);
-  base::TimeDelta time_left_in_policy;
-  if (last_input_process_time_on_main_.is_null() &&
-      !task_queue_manager_->IsQueueEmpty(COMPOSITOR_TASK_QUEUE)) {
-    // If the input event is still pending, go into input prioritized policy
-    // and check again later.
-    time_left_in_policy = escalated_priority_duration;
-  } else {
-    // Otherwise make sure the input prioritization policy ends on time.
-    base::TimeTicks new_priority_end(
-        std::max(last_input_receipt_time_on_compositor_,
-                 last_input_process_time_on_main_) +
-        escalated_priority_duration);
-    time_left_in_policy = new_priority_end - now;
-  }
-  return time_left_in_policy;
-}
-
-RendererSchedulerImpl::IdlePeriodState
-RendererSchedulerImpl::ComputeNewLongIdlePeriodState(
+SchedulerHelper::IdlePeriodState SchedulerHelper::ComputeNewLongIdlePeriodState(
     const base::TimeTicks now,
     base::TimeDelta* next_long_idle_period_delay_out) {
-  DCHECK(main_thread_checker_.CalledOnValidThread());
+  CheckOnValidThread();
 
-  MaybeUpdatePolicy();
-  if (SchedulerPolicy() == Policy::TOUCHSTART_PRIORITY) {
-    // Don't start a long idle task in touch start priority, try again when
-    // the policy is scheduled to end.
-    *next_long_idle_period_delay_out = current_policy_expiration_time_ - now;
+  if (!scheduler_helper_delegate_->CanEnterLongIdlePeriod(
+          now, next_long_idle_period_delay_out)) {
     return IdlePeriodState::NOT_IN_IDLE_PERIOD;
   }
 
@@ -455,10 +143,9 @@ RendererSchedulerImpl::ComputeNewLongIdlePeriodState(
   }
 }
 
-void RendererSchedulerImpl::InitiateLongIdlePeriod() {
-  TRACE_EVENT0(TRACE_DISABLED_BY_DEFAULT("renderer.scheduler"),
-               "InitiateLongIdlePeriod");
-  DCHECK(main_thread_checker_.CalledOnValidThread());
+void SchedulerHelper::InitiateLongIdlePeriod() {
+  TRACE_EVENT0(disabled_by_default_tracing_category_, "InitiateLongIdlePeriod");
+  CheckOnValidThread();
 
   // End any previous idle period.
   EndIdlePeriod();
@@ -468,11 +155,11 @@ void RendererSchedulerImpl::InitiateLongIdlePeriod() {
   IdlePeriodState new_idle_period_state =
       ComputeNewLongIdlePeriodState(now, &next_long_idle_period_delay);
   if (IsInIdlePeriod(new_idle_period_state)) {
-    estimated_next_frame_begin_ = now + next_long_idle_period_delay;
+    estimated_end_of_idle_ = now + next_long_idle_period_delay;
     StartIdlePeriod(new_idle_period_state);
   }
 
-  if (task_queue_manager_->IsQueueEmpty(IDLE_TASK_QUEUE)) {
+  if (task_queue_manager_->IsQueueEmpty(QueueId::IDLE_TASK_QUEUE)) {
     // If there are no current idle tasks then post the call to initiate the
     // next idle for execution after wakeup (at which point after-wakeup idle
     // tasks might be eligible to run or more idle tasks posted).
@@ -483,23 +170,22 @@ void RendererSchedulerImpl::InitiateLongIdlePeriod() {
   } else {
     // Otherwise post on the normal control task queue.
     control_task_runner_->PostDelayedTask(
-        FROM_HERE,
-        initiate_next_long_idle_period_closure_.callback(),
+        FROM_HERE, initiate_next_long_idle_period_closure_.callback(),
         next_long_idle_period_delay);
   }
 }
 
-void RendererSchedulerImpl::InitiateLongIdlePeriodAfterWakeup() {
-  TRACE_EVENT0(TRACE_DISABLED_BY_DEFAULT("renderer.scheduler"),
+void SchedulerHelper::InitiateLongIdlePeriodAfterWakeup() {
+  TRACE_EVENT0(disabled_by_default_tracing_category_,
                "InitiateLongIdlePeriodAfterWakeup");
-  DCHECK(main_thread_checker_.CalledOnValidThread());
+  CheckOnValidThread();
 
   if (IsInIdlePeriod(idle_period_state_)) {
     // Since we were asleep until now, end the async idle period trace event at
     // the time when it would have ended were we awake.
     TRACE_EVENT_ASYNC_END_WITH_TIMESTAMP0(
-        "renderer.scheduler", "RendererSchedulerIdlePeriod", this,
-        std::min(estimated_next_frame_begin_, Now()).ToInternalValue());
+        tracing_category_, "RendererSchedulerIdlePeriod", this,
+        std::min(estimated_end_of_idle_, Now()).ToInternalValue());
     idle_period_state_ = IdlePeriodState::ENDING_LONG_IDLE_PERIOD;
     EndIdlePeriod();
   }
@@ -509,24 +195,24 @@ void RendererSchedulerImpl::InitiateLongIdlePeriodAfterWakeup() {
   // on the idle task queue before the next idle period starts so they are
   // eligible to be run during the new idle period.
   control_task_runner_->PostTask(
-      FROM_HERE,
-      initiate_next_long_idle_period_closure_.callback());
+      FROM_HERE, initiate_next_long_idle_period_closure_.callback());
 }
 
-void RendererSchedulerImpl::StartIdlePeriod(IdlePeriodState new_state) {
-  TRACE_EVENT_ASYNC_BEGIN0("renderer.scheduler",
-                           "RendererSchedulerIdlePeriod", this);
-  DCHECK(main_thread_checker_.CalledOnValidThread());
+void SchedulerHelper::StartIdlePeriod(IdlePeriodState new_state) {
+  TRACE_EVENT_ASYNC_BEGIN0(tracing_category_, "RendererSchedulerIdlePeriod",
+                           this);
+  CheckOnValidThread();
   DCHECK(IsInIdlePeriod(new_state));
 
-  renderer_task_queue_selector_->EnableQueue(
-      IDLE_TASK_QUEUE, RendererTaskQueueSelector::BEST_EFFORT_PRIORITY);
-  task_queue_manager_->PumpQueue(IDLE_TASK_QUEUE);
+  task_queue_selector_->EnableQueue(
+      QueueId::IDLE_TASK_QUEUE,
+      PrioritizingTaskQueueSelector::BEST_EFFORT_PRIORITY);
+  task_queue_manager_->PumpQueue(QueueId::IDLE_TASK_QUEUE);
   idle_period_state_ = new_state;
 }
 
-void RendererSchedulerImpl::EndIdlePeriod() {
-  DCHECK(main_thread_checker_.CalledOnValidThread());
+void SchedulerHelper::EndIdlePeriod() {
+  CheckOnValidThread();
 
   end_idle_period_closure_.Cancel();
   initiate_next_long_idle_period_closure_.Cancel();
@@ -540,79 +226,81 @@ void RendererSchedulerImpl::EndIdlePeriod() {
   // trace event.
   if (idle_period_state_ != IdlePeriodState::ENDING_LONG_IDLE_PERIOD) {
     bool is_tracing;
-    TRACE_EVENT_CATEGORY_GROUP_ENABLED("renderer.scheduler", &is_tracing);
-    if (is_tracing && !estimated_next_frame_begin_.is_null() &&
-        base::TimeTicks::Now() > estimated_next_frame_begin_) {
+    TRACE_EVENT_CATEGORY_GROUP_ENABLED(tracing_category_, &is_tracing);
+    if (is_tracing && !estimated_end_of_idle_.is_null() &&
+        base::TimeTicks::Now() > estimated_end_of_idle_) {
       TRACE_EVENT_ASYNC_STEP_INTO_WITH_TIMESTAMP0(
-          "renderer.scheduler",
-          "RendererSchedulerIdlePeriod",
-          this,
-          "DeadlineOverrun",
-          estimated_next_frame_begin_.ToInternalValue());
+          tracing_category_, "RendererSchedulerIdlePeriod", this,
+          "DeadlineOverrun", estimated_end_of_idle_.ToInternalValue());
     }
-    TRACE_EVENT_ASYNC_END0("renderer.scheduler",
-                           "RendererSchedulerIdlePeriod", this);
+    TRACE_EVENT_ASYNC_END0(tracing_category_, "RendererSchedulerIdlePeriod",
+                           this);
   }
 
-  renderer_task_queue_selector_->DisableQueue(IDLE_TASK_QUEUE);
+  task_queue_selector_->DisableQueue(QueueId::IDLE_TASK_QUEUE);
   idle_period_state_ = IdlePeriodState::NOT_IN_IDLE_PERIOD;
 }
 
 // static
-bool RendererSchedulerImpl::IsInIdlePeriod(IdlePeriodState state) {
+bool SchedulerHelper::IsInIdlePeriod(IdlePeriodState state) {
   return state != IdlePeriodState::NOT_IN_IDLE_PERIOD;
 }
 
-bool RendererSchedulerImpl::CanExceedIdleDeadlineIfRequired() const {
-  TRACE_EVENT_BEGIN0("renderer.scheduler", "CanExceedIdleDeadlineIfRequired");
-  DCHECK(main_thread_checker_.CalledOnValidThread());
+bool SchedulerHelper::CanExceedIdleDeadlineIfRequired() const {
+  TRACE_EVENT_BEGIN0(tracing_category_, "CanExceedIdleDeadlineIfRequired");
+  CheckOnValidThread();
   return idle_period_state_ ==
          IdlePeriodState::IN_LONG_IDLE_PERIOD_WITH_MAX_DEADLINE;
 }
 
-void RendererSchedulerImpl::SetTimeSourceForTesting(
+void SchedulerHelper::SetTimeSourceForTesting(
     scoped_refptr<cc::TestNowSource> time_source) {
-  DCHECK(main_thread_checker_.CalledOnValidThread());
+  CheckOnValidThread();
   time_source_ = time_source;
   task_queue_manager_->SetTimeSourceForTesting(time_source);
 }
 
-void RendererSchedulerImpl::SetWorkBatchSizeForTesting(size_t work_batch_size) {
-  DCHECK(main_thread_checker_.CalledOnValidThread());
+void SchedulerHelper::SetWorkBatchSizeForTesting(size_t work_batch_size) {
+  CheckOnValidThread();
   task_queue_manager_->SetWorkBatchSize(work_batch_size);
 }
 
-base::TimeTicks RendererSchedulerImpl::Now() const {
+base::TimeTicks SchedulerHelper::Now() const {
   return UNLIKELY(time_source_) ? time_source_->Now() : base::TimeTicks::Now();
 }
 
-RendererSchedulerImpl::PollableNeedsUpdateFlag::PollableNeedsUpdateFlag(
-    base::Lock* write_lock_)
-    : flag_(false), write_lock_(write_lock_) {
+base::TimeTicks SchedulerHelper::EstimatedEndOfIdle() const {
+  return estimated_end_of_idle_;
+}
+
+void SchedulerHelper::SetEstimatedEndOfIdle(
+    base::TimeTicks estimated_next_frame_begin) {
+  estimated_end_of_idle_ = estimated_next_frame_begin;
+}
+
+const CancelableClosureHolder& SchedulerHelper::EndIdlePeriodClosure() const {
+  return end_idle_period_closure_;
 }
 
-RendererSchedulerImpl::PollableNeedsUpdateFlag::~PollableNeedsUpdateFlag() {
+SchedulerHelper::IdlePeriodState
+SchedulerHelper::SchedulerIdlePeriodState() const {
+  return idle_period_state_;
 }
 
-void RendererSchedulerImpl::PollableNeedsUpdateFlag::SetWhileLocked(
-    bool value) {
-  write_lock_->AssertAcquired();
-  base::subtle::Release_Store(&flag_, value);
+PrioritizingTaskQueueSelector* SchedulerHelper::SchedulerTaskQueueSelector()
+    const {
+  return task_queue_selector_.get();
 }
 
-bool RendererSchedulerImpl::PollableNeedsUpdateFlag::IsSet() const {
-  return base::subtle::Acquire_Load(&flag_) != 0;
+TaskQueueManager* SchedulerHelper::SchedulerTaskQueueManager() const {
+  return task_queue_manager_.get();
 }
 
 // static
-const char* RendererSchedulerImpl::TaskQueueIdToString(QueueId queue_id) {
+const char* SchedulerHelper::TaskQueueIdToString(QueueId queue_id) {
   switch (queue_id) {
     case DEFAULT_TASK_QUEUE:
       return "default_tq";
-    case COMPOSITOR_TASK_QUEUE:
-      return "compositor_tq";
-    case LOADING_TASK_QUEUE:
-      return "loading_tq";
     case IDLE_TASK_QUEUE:
       return "idle_tq";
     case CONTROL_TASK_QUEUE:
@@ -626,36 +314,7 @@ const char* RendererSchedulerImpl::TaskQueueIdToString(QueueId queue_id) {
 }
 
 // static
-const char* RendererSchedulerImpl::PolicyToString(Policy policy) {
-  switch (policy) {
-    case Policy::NORMAL:
-      return "normal";
-    case Policy::COMPOSITOR_PRIORITY:
-      return "compositor";
-    case Policy::TOUCHSTART_PRIORITY:
-      return "touchstart";
-    default:
-      NOTREACHED();
-      return nullptr;
-  }
-}
-
-const char* RendererSchedulerImpl::InputStreamStateToString(
-    InputStreamState state) {
-  switch (state) {
-    case InputStreamState::INACTIVE:
-      return "inactive";
-    case InputStreamState::ACTIVE:
-      return "active";
-    case InputStreamState::ACTIVE_AND_AWAITING_TOUCHSTART_RESPONSE:
-      return "active_and_awaiting_touchstart_response";
-    default:
-      NOTREACHED();
-      return nullptr;
-  }
-}
-
-const char* RendererSchedulerImpl::IdlePeriodStateToString(
+const char* SchedulerHelper::IdlePeriodStateToString(
     IdlePeriodState idle_period_state) {
   switch (idle_period_state) {
     case IdlePeriodState::NOT_IN_IDLE_PERIOD:
@@ -674,81 +333,16 @@ const char* RendererSchedulerImpl::IdlePeriodStateToString(
   }
 }
 
-scoped_refptr<base::trace_event::ConvertableToTraceFormat>
-RendererSchedulerImpl::AsValueLocked(base::TimeTicks optional_now) const {
-  DCHECK(main_thread_checker_.CalledOnValidThread());
-  incoming_signals_lock_.AssertAcquired();
-
-  if (optional_now.is_null())
-    optional_now = Now();
-  scoped_refptr<base::trace_event::TracedValue> state =
-      new base::trace_event::TracedValue();
-
-  state->SetString("current_policy", PolicyToString(current_policy_));
-  state->SetString("idle_period_state",
-                   IdlePeriodStateToString(idle_period_state_));
-  state->SetString("input_stream_state",
-                   InputStreamStateToString(input_stream_state_));
-  state->SetDouble("now", (optional_now - base::TimeTicks()).InMillisecondsF());
-  state->SetDouble("last_input_receipt_time_on_compositor_",
-                   (last_input_receipt_time_on_compositor_ - base::TimeTicks())
-                       .InMillisecondsF());
-  state->SetDouble(
-      "last_input_process_time_on_main_",
-      (last_input_process_time_on_main_ - base::TimeTicks()).InMillisecondsF());
-  state->SetDouble(
-      "estimated_next_frame_begin",
-      (estimated_next_frame_begin_ - base::TimeTicks()).InMillisecondsF());
-
-  return state;
-}
-
-RendererSchedulerImpl::InputStreamState
-RendererSchedulerImpl::ComputeNewInputStreamState(
-    InputStreamState current_state,
-    blink::WebInputEvent::Type new_input_type,
-    blink::WebInputEvent::Type last_input_type) {
-  switch (new_input_type) {
-    case blink::WebInputEvent::TouchStart:
-      return InputStreamState::ACTIVE_AND_AWAITING_TOUCHSTART_RESPONSE;
-
-    case blink::WebInputEvent::TouchMove:
-      // Observation of consecutive touchmoves is a strong signal that the page
-      // is consuming the touch sequence, in which case touchstart response
-      // prioritization is no longer necessary. Otherwise, the initial touchmove
-      // should preserve the touchstart response pending state.
-      if (current_state ==
-          InputStreamState::ACTIVE_AND_AWAITING_TOUCHSTART_RESPONSE) {
-        return last_input_type == blink::WebInputEvent::TouchMove
-                   ? InputStreamState::ACTIVE
-                   : InputStreamState::ACTIVE_AND_AWAITING_TOUCHSTART_RESPONSE;
-      }
-      break;
-
-    case blink::WebInputEvent::GestureTapDown:
-    case blink::WebInputEvent::GestureShowPress:
-    case blink::WebInputEvent::GestureFlingCancel:
-    case blink::WebInputEvent::GestureScrollEnd:
-      // With no observable effect, these meta events do not indicate a
-      // meaningful touchstart response and should not impact task priority.
-      return current_state;
-
-    default:
-      break;
-  }
-  return InputStreamState::ACTIVE;
-}
-
-void RendererSchedulerImpl::AddTaskObserver(
+void SchedulerHelper::AddTaskObserver(
     base::MessageLoop::TaskObserver* task_observer) {
-  DCHECK(main_thread_checker_.CalledOnValidThread());
+  CheckOnValidThread();
   if (task_queue_manager_)
     task_queue_manager_->AddTaskObserver(task_observer);
 }
 
-void RendererSchedulerImpl::RemoveTaskObserver(
+void SchedulerHelper::RemoveTaskObserver(
     base::MessageLoop::TaskObserver* task_observer) {
-  DCHECK(main_thread_checker_.CalledOnValidThread());
+  CheckOnValidThread();
   if (task_queue_manager_)
     task_queue_manager_->RemoveTaskObserver(task_observer);
 }