EXPERIMENTAL, Trying Ross's suggestion

content/renderer/scheduler/task_queue_manager.cc

Index: content/renderer/scheduler/task_queue_manager.cc
diff --git a/content/renderer/scheduler/task_queue_manager.cc b/content/renderer/scheduler/task_queue_manager.cc
index f4f8fc5f8f28a2ee01e57836107ff7658dab50df..1d394049197dda69c1ff7b4991604b572d5763f1 100644
--- a/content/renderer/scheduler/task_queue_manager.cc
+++ b/content/renderer/scheduler/task_queue_manager.cc
@@ -5,6 +5,7 @@
 #include "content/renderer/scheduler/task_queue_manager.h"
 
 #include <queue>
+#include <set>
 
 #include "base/bind.h"
 #include "base/trace_event/trace_event.h"
@@ -67,10 +68,11 @@ class TaskQueue : public base::SingleThreadTaskRunner {
                            base::TimeDelta delay,
                            TaskType task_type);
 
-  // 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);
+  // Adds delayed_task_queue_.top() 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 EnqueueNextPendingTask();
 
   void PumpQueueLocked();
   bool ShouldAutoPumpQueueLocked(
@@ -91,9 +93,7 @@ class TaskQueue : public base::SingleThreadTaskRunner {
   base::TaskQueue incoming_queue_;
   TaskQueueManager::PumpPolicy pump_policy_;
   const char* name_;
-  std::priority_queue<base::TimeTicks,
-                      std::vector<base::TimeTicks>,
-                      std::greater<base::TimeTicks>> delayed_task_run_times_;
+  base::DelayedTaskQueue delayed_task_queue_;
 
   base::TaskQueue work_queue_;
 
@@ -112,6 +112,11 @@ TaskQueue::~TaskQueue() {
 void TaskQueue::WillDeleteTaskQueueManager() {
   base::AutoLock lock(lock_);
   task_queue_manager_ = nullptr;
+
+  // Clear all delayed tasks because we need them to be deleted before the blink
+  // heap goes away.
+  while (!delayed_task_queue_.empty())
+    delayed_task_queue_.pop();
 }
 
 bool TaskQueue::RunsTasksOnCurrentThread() const {
@@ -135,9 +140,9 @@ bool TaskQueue::PostDelayedTaskImpl(const tracked_objects::Location& from_here,
 
   if (delay > base::TimeDelta()) {
     pending_task.delayed_run_time = task_queue_manager_->Now() + delay;
-    delayed_task_run_times_.push(pending_task.delayed_run_time);
+    delayed_task_queue_.push(pending_task);
     return task_queue_manager_->PostDelayedTask(
-        FROM_HERE, Bind(&TaskQueue::EnqueueTask, this, pending_task), delay);
+        FROM_HERE, Bind(&TaskQueue::EnqueueNextPendingTask, this), delay);
   }
   EnqueueTaskLocked(pending_task);
   return true;
@@ -174,9 +179,10 @@ bool TaskQueue::UpdateWorkQueue(
 
   {
     base::AutoLock lock(lock_);
-    if (!delayed_task_run_times_.empty()) {
+    if (!delayed_task_queue_.empty()) {
       *next_pending_delayed_task =
-          std::min(*next_pending_delayed_task, delayed_task_run_times_.top());
+          std::min(*next_pending_delayed_task,
+                   delayed_task_queue_.top().delayed_run_time);
     }
     if (!ShouldAutoPumpQueueLocked(event_type))
       return false;
@@ -209,9 +215,16 @@ void TaskQueue::TraceQueueSize(bool is_locked) const {
     lock_.Release();
 }
 
-void TaskQueue::EnqueueTask(const base::PendingTask& pending_task) {
+void TaskQueue::EnqueueNextPendingTask() {
   base::AutoLock lock(lock_);
-  EnqueueTaskLocked(pending_task);
+  if (!task_queue_manager_)
+    return;
+
+  if (delayed_task_queue_.empty())
+    return;
+
+  EnqueueTaskLocked(delayed_task_queue_.top());
+  delayed_task_queue_.pop();
 }
 
 void TaskQueue::EnqueueTaskLocked(const base::PendingTask& pending_task) {
@@ -224,11 +237,6 @@ void TaskQueue::EnqueueTaskLocked(const base::PendingTask& pending_task) {
   incoming_queue_.push(pending_task);
 
   if (!pending_task.delayed_run_time.is_null()) {
-    // Update the time of the next pending delayed task.
-    while (!delayed_task_run_times_.empty() &&
-           delayed_task_run_times_.top() <= pending_task.delayed_run_time) {
-      delayed_task_run_times_.pop();
-    }
     // Clear the delayed run time because we've already applied the delay
     // before getting here.
     incoming_queue_.back().delayed_run_time = base::TimeTicks();