[content]: Add support for long idle times in the Blink Scheduler.

content/renderer/scheduler/task_queue_manager.cc

 // Copyright 2014 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/task_queue_manager.h"
 
 #include <queue>
 
 #include "base/bind.h"
 #include "base/trace_event/trace_event.h"
@@ skipping 24 matching lines @@
                                   const base::Closure& task,
                                   base::TimeDelta delay) override {
     return PostDelayedTaskImpl(from_here, task, delay, TaskType::NON_NESTABLE);
   }
 
   bool IsQueueEmpty() const;
 
   void SetPumpPolicy(TaskQueueManager::PumpPolicy pump_policy);
   void PumpQueue();
 
+  void GetNextPendingDelayedTask(base::TimeTicks* next_pending_delayed_task);
+
   bool UpdateWorkQueue(base::TimeTicks* next_pending_delayed_task,
                        const base::PendingTask* previous_task);
   base::PendingTask TakeTaskFromWorkQueue();
 
   void WillDeleteTaskQueueManager();
 
   base::TaskQueue& work_queue() { return work_queue_; }
 
   void set_name(const char* name) { name_ = name; }
 
@@ skipping 14 matching lines @@
 
   // Adds a task at the end of the incoming task queue and schedules a call to
   // TaskQueueManager::DoWork() if the incoming queue was empty and automatic
   // pumping is enabled. Can be called on an arbitrary thread.
   void EnqueueTask(const base::PendingTask& pending_task);
 
   void PumpQueueLocked();
   bool TaskIsOlderThanQueuedTasks(const base::PendingTask* task);
   bool ShouldAutoPumpQueueLocked(const base::PendingTask* previous_task);
   void EnqueueTaskLocked(const base::PendingTask& pending_task);
+  void GetNextPendingDelayedTaskLocked(
+      base::TimeTicks* next_pending_delayed_task);
 
   void TraceQueueSize(bool is_locked) const;
   static const char* PumpPolicyToString(
       TaskQueueManager::PumpPolicy pump_policy);
   static void QueueAsValueInto(const base::TaskQueue& queue,
                                base::trace_event::TracedValue* state);
   static void TaskAsValueInto(const base::PendingTask& task,
                               base::trace_event::TracedValue* state);
 
   // This lock protects all members except the work queue.
@@ skipping 90 matching lines @@
   if (pump_policy_ == TaskQueueManager::PumpPolicy::MANUAL)
     return false;
   if (pump_policy_ == TaskQueueManager::PumpPolicy::AFTER_WAKEUP &&
       TaskIsOlderThanQueuedTasks(previous_task))
     return false;
   if (incoming_queue_.empty())
     return false;
   return true;
 }
 
+void TaskQueue::GetNextPendingDelayedTask(
+    base::TimeTicks* next_pending_delayed_task) {
+  base::AutoLock lock(lock_);
+  GetNextPendingDelayedTaskLocked(next_pending_delayed_task);
+}
+
+void TaskQueue::GetNextPendingDelayedTaskLocked(

[picksi, 2015/03/04 10:43:23]

Can this deal better with the delayed_task_run_times being empty? It's silent
"failure" could lead to trouble. Maybe it should return a success bool?

[rmcilroy, 2015/03/04 14:23:12]

Done.

+    base::TimeTicks* next_pending_delayed_task) {
+  lock_.AssertAcquired();
+  if (!delayed_task_run_times_.empty()) {
+    *next_pending_delayed_task =
+        std::min(*next_pending_delayed_task, delayed_task_run_times_.top());
+  }
+}
+
 bool TaskQueue::UpdateWorkQueue(
     base::TimeTicks* next_pending_delayed_task,
     const base::PendingTask* previous_task) {
   if (!work_queue_.empty())
     return true;
 
   {
     base::AutoLock lock(lock_);
-    if (!delayed_task_run_times_.empty()) {
-      *next_pending_delayed_task =
-          std::min(*next_pending_delayed_task, delayed_task_run_times_.top());
-    }
+    GetNextPendingDelayedTaskLocked(next_pending_delayed_task);
     if (!ShouldAutoPumpQueueLocked(previous_task))
       return false;
     work_queue_.Swap(&incoming_queue_);
     TraceQueueSize(true);
     return true;
   }
 }
 
 base::PendingTask TaskQueue::TakeTaskFromWorkQueue() {
   base::PendingTask pending_task = work_queue_.front();
@@ skipping 170 matching lines @@
 scoped_refptr<base::SingleThreadTaskRunner>
 TaskQueueManager::TaskRunnerForQueue(size_t queue_index) const {
   return Queue(queue_index);
 }
 
 bool TaskQueueManager::IsQueueEmpty(size_t queue_index) const {
   internal::TaskQueue* queue = Queue(queue_index);
   return queue->IsQueueEmpty();
 }
 
+base::TimeTicks TaskQueueManager::NextPendingDelayedTask() {
+  DCHECK(main_thread_checker_.CalledOnValidThread());
+  base::TimeTicks next_pending_delayed_task(
+      base::TimeTicks::FromInternalValue(kMaxTimeTicks));
+  for (auto& queue : queues_) {
+    queue->GetNextPendingDelayedTask(&next_pending_delayed_task);
+  }
+
+  if (next_pending_delayed_task ==

[picksi, 2015/03/04 10:43:22]

If I understand the code, this check for unchanged-time looks fragile to me
(i.e. what would happen if GetNextPendingDelayedTask returned kMaxTimeTicks
coincidentally?).

[rmcilroy, 2015/03/04 14:23:12]

Done (although we don't really need to worry about this ever happening until a
task is posted for Sun, 4 December 292,277,026,596 ;)).

[picksi, 2015/03/04 16:29:05]

I suppose the heat death of the universe will be a more pressing issue than a
glitch in some ancient software, but I definitely prefer the way it looks now!

+      base::TimeTicks::FromInternalValue(kMaxTimeTicks))
+    return base::TimeTicks();
+
+  return next_pending_delayed_task;
+}
+
 void TaskQueueManager::SetPumpPolicy(size_t queue_index,
                                      PumpPolicy pump_policy) {
   DCHECK(main_thread_checker_.CalledOnValidThread());
   internal::TaskQueue* queue = Queue(queue_index);
   queue->SetPumpPolicy(pump_policy);
 }
 
 void TaskQueueManager::PumpQueue(size_t queue_index) {
   DCHECK(main_thread_checker_.CalledOnValidThread());
   internal::TaskQueue* queue = Queue(queue_index);
@@ skipping 174 matching lines @@
   state->EndArray();
   state->BeginDictionary("selector");
   selector_->AsValueInto(state.get());
   state->EndDictionary();
   if (should_run)
     state->SetInteger("selected_queue", selected_queue);
   return state;
 }
 
 }  // namespace content