Move and rename TaskTimeTracker to public interface exposed to WebThread, use in WebPerf Agent.

third_party/WebKit/Source/platform/scheduler/base/task_queue_manager.cc

Index: third_party/WebKit/Source/platform/scheduler/base/task_queue_manager.cc
diff --git a/third_party/WebKit/Source/platform/scheduler/base/task_queue_manager.cc b/third_party/WebKit/Source/platform/scheduler/base/task_queue_manager.cc
index 31adb7257af790faa8ed72b0ed0487afd98a3768..b945da63b78e027c5284e1f8ff18011582cd8be9 100644
--- a/third_party/WebKit/Source/platform/scheduler/base/task_queue_manager.cc
+++ b/third_party/WebKit/Source/platform/scheduler/base/task_queue_manager.cc
@@ -34,6 +34,11 @@ void RecordImmediateTaskQueueingDuration(tracked_objects::Duration duration) {
       "RendererScheduler.TaskQueueManager.ImmediateTaskQueueingDuration",
       base::TimeDelta::FromMilliseconds(duration.InMilliseconds()));
 }
+
+double MonotonicTimeInSeconds(base::TimeTicks timeTicks) {
+  return (timeTicks.ToInternalValue() / static_cast<double>(
+      base::Time::kMicrosecondsPerSecond));
+}
 }
 
 TaskQueueManager::TaskQueueManager(
@@ -47,6 +52,7 @@ TaskQueueManager::TaskQueueManager(
       work_batch_size_(1),
       task_count_(0),
       task_time_tracker_(nullptr),
+      task_time_observer_(nullptr),
       tracing_category_(tracing_category),
       disabled_by_default_tracing_category_(
           disabled_by_default_tracing_category),
@@ -215,7 +221,14 @@ void TaskQueueManager::DoWork(base::TimeTicks run_time, bool from_main_thread) {
     bool should_trigger_wakeup = work_queue->task_queue()->wakeup_policy() ==
                                  TaskQueue::WakeupPolicy::CAN_WAKE_OTHER_QUEUES;
 
-    switch (ProcessTaskFromWorkQueue(work_queue, &previous_task)) {
+    if (!delegate_->IsNested() && task_time_observer_)
+      task_time_observer_->willProcessTask();
+    TaskQueueManager::ProcessTaskResult result = ProcessTaskFromWorkQueue(
+        work_queue, &previous_task);
+    if (!delegate_->IsNested() && task_time_observer_)
+      task_time_observer_->didProcessTask();
+
+    switch (result) {
       case ProcessTaskResult::DEFERRED:
         // If a task was deferred, try again with another task. Note that this
         // means deferred tasks (i.e. non-nestable tasks) will never trigger
@@ -232,6 +245,10 @@ void TaskQueueManager::DoWork(base::TimeTicks run_time, bool from_main_thread) {
       // Only report top level task durations.
       base::TimeTicks task_end_time = lazy_now.Now();
       task_time_tracker_->ReportTaskTime(task_start_time, task_end_time);
+      if (task_time_observer_)
+          task_time_observer_->reportTaskTime(
+              MonotonicTimeInSeconds(task_start_time),
+              MonotonicTimeInSeconds(task_end_time));
       task_start_time = task_end_time;
     }