Move throttling of background timers into the renderer scheduler

components/scheduler/renderer/throttling_helper.cc

Index: components/scheduler/renderer/throttling_helper.cc
diff --git a/components/scheduler/renderer/throttling_helper.cc b/components/scheduler/renderer/throttling_helper.cc
new file mode 100644
index 0000000000000000000000000000000000000000..cd343c6ccd4dd077fe38aec562e44ba561f2d8b2
--- /dev/null
+++ b/components/scheduler/renderer/throttling_helper.cc
@@ -0,0 +1,120 @@
+// 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/throttling_helper.h"
+
+#include "base/logging.h"
+#include "components/scheduler/base/real_time_domain.h"
+#include "components/scheduler/base/virtual_time_domain.h"
+#include "components/scheduler/child/scheduler_tqm_delegate.h"
+#include "components/scheduler/renderer/renderer_scheduler_impl.h"
+#include "components/scheduler/renderer/web_frame_scheduler_impl.h"
+#include "third_party/WebKit/public/platform/WebFrameScheduler.h"
+
+namespace scheduler {
+
+ThrottlingHelper::ThrottlingHelper(RendererSchedulerImpl* renderer_scheduler,
+                                   const char* tracing_category)
+    : task_runner_(renderer_scheduler->ControlTaskRunner()),
+      renderer_scheduler_(renderer_scheduler),
+      tick_clock_(renderer_scheduler->tick_clock()),
+      tracing_category_(tracing_category),
+      time_domain_(new VirtualTimeDomain(this, tick_clock_->NowTicks())),
+      pending_pump_throttled_tasks_(false),
+      work_to_do_(false),
+      weak_factory_(this) {
+  pump_throttled_tasks_closure_ = base::Bind(
+      &ThrottlingHelper::PumpThrottledTasks, weak_factory_.GetWeakPtr());
+  forward_immediate_work_closure_ =
+      base::Bind(&ThrottlingHelper::OnTimeDomainHasImmediateWork,
+                 weak_factory_.GetWeakPtr());
+  renderer_scheduler_->RegisterTimeDomain(time_domain_);
+}
+
+ThrottlingHelper::~ThrottlingHelper() {
+  renderer_scheduler_->UnregisterTimeDomain(time_domain_);
+}
+
+void ThrottlingHelper::Throttle(TaskQueue* task_queue) {
+  throttled_queues_.insert(task_queue);
+
+  task_queue->SetTimeDomain(time_domain_);
+  task_queue->SetPumpPolicy(TaskQueue::PumpPolicy::MANUAL);
+
+  work_to_do_ |= task_queue->HasPendingImmediateTask();
+  work_to_do_ |= task_queue->HasPendingDelayedTask();
+
+  MaybeSchedulePumpThrottledTasksLocked();
+}
+
+void ThrottlingHelper::Unthrottle(TaskQueue* task_queue) {
+  throttled_queues_.erase(task_queue);
+
+  task_queue->SetTimeDomain(renderer_scheduler_->real_time_domain());
+  task_queue->SetPumpPolicy(TaskQueue::PumpPolicy::AUTO);
+  if (throttled_queues_.empty())
+    work_to_do_ = false;
+}
+
+void ThrottlingHelper::Unregister(TaskQueue* task_queue) {
+  throttled_queues_.erase(task_queue);
+

[Sami, 2015/11/25 17:12:25]

DCHECK that the task queue isn't still in the virtual time domain?

[alex clarke (OOO till 29th), 2015/11/26 18:43:27]

Acknowledged.

+  if (throttled_queues_.empty())
+    work_to_do_ = false;
+}
+
+void ThrottlingHelper::OnTimeDomainHasImmediateWork() {
+  // Forward to the main thread if called from another thread.
+  if (!task_runner_->RunsTasksOnCurrentThread()) {
+    task_runner_->PostTask(FROM_HERE, forward_immediate_work_closure_);
+    return;
+  }
+  TRACE_EVENT0(tracing_category_,
+               "ThrottlingHelper::OnTimeDomainHasImmediateWork");
+  work_to_do_ = true;
+  MaybeSchedulePumpThrottledTasksLocked();
+}
+
+void ThrottlingHelper::OnTimeDomainHasDelayedWork() {
+  TRACE_EVENT0(tracing_category_,
+               "ThrottlingHelper::OnTimeDomainHasDelayedWork");
+  work_to_do_ = true;
+  MaybeSchedulePumpThrottledTasksLocked();
+}
+
+void ThrottlingHelper::PumpThrottledTasks() {
+  TRACE_EVENT0(tracing_category_, "ThrottlingHelper::PumpThrottledTasks");
+  pending_pump_throttled_tasks_ = false;
+
+  time_domain_->AdvanceTo(tick_clock_->NowTicks());
+  work_to_do_ = false;

[Sami, 2015/11/25 17:12:25]

Do we need this flag? Won't OnTimeDomainHasImmediateWork or
OnTimeDomainHasDelayedWork always be called when there are things to do, and
we'd only need to make sure we've scheduled a pump?

[alex clarke (OOO till 29th), 2015/11/26 18:43:27]

Done.

+  for (TaskQueue* task_queue : throttled_queues_) {
+    if (task_queue->HasPendingImmediateTask() ||
+        task_queue->HasPendingDelayedTask()) {
+      task_queue->PumpQueue();
+      work_to_do_ = true;
+    }
+  }
+
+  MaybeSchedulePumpThrottledTasksLocked();
+}
+
+/* static */
+base::TimeDelta ThrottlingHelper::DelayToNextRunTimeInSeconds(
+    base::TimeTicks now) {
+  const base::TimeDelta one_second = base::TimeDelta::FromSeconds(1);
+  return one_second - ((now - base::TimeTicks()) % one_second);
+}
+
+void ThrottlingHelper::MaybeSchedulePumpThrottledTasksLocked() {
+  if (pending_pump_throttled_tasks_ || !work_to_do_)
+    return;
+
+  pending_pump_throttled_tasks_ = true;
+  task_runner_->PostDelayedTask(
+      FROM_HERE, pump_throttled_tasks_closure_,
+      DelayToNextRunTimeInSeconds(tick_clock_->NowTicks()));
+}
+
+}  // namespace scheduler