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..313e28c3767a0cb54cc3e49b8ffc873ce17a7c8c 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
@@ -14,9 +14,9 @@
 #include "platform/scheduler/base/task_queue_impl.h"
 #include "platform/scheduler/base/task_queue_manager_delegate.h"
 #include "platform/scheduler/base/task_queue_selector.h"
-#include "platform/scheduler/base/task_time_tracker.h"
 #include "platform/scheduler/base/work_queue.h"
 #include "platform/scheduler/base/work_queue_sets.h"
+#include "public/platform/scheduler/base/task_time_observer.h"
 
 namespace blink {
 namespace scheduler {
@@ -34,6 +34,10 @@ void RecordImmediateTaskQueueingDuration(tracked_objects::Duration duration) {
       "RendererScheduler.TaskQueueManager.ImmediateTaskQueueingDuration",
       base::TimeDelta::FromMilliseconds(duration.InMilliseconds()));
 }
+
+double MonotonicTimeInSeconds(base::TimeTicks timeTicks) {
+  return (timeTicks - base::TimeTicks()).InSecondsF();
+}
 }
 
 TaskQueueManager::TaskQueueManager(
@@ -46,7 +50,6 @@ TaskQueueManager::TaskQueueManager(
       task_was_run_on_quiescence_monitored_queue_(false),
       work_batch_size_(1),
       task_count_(0),
-      task_time_tracker_(nullptr),
       tracing_category_(tracing_category),
       disabled_by_default_tracing_category_(
           disabled_by_default_tracing_category),
@@ -195,9 +198,9 @@ void TaskQueueManager::DoWork(base::TimeTicks run_time, bool from_main_thread) {
     queues_to_delete_.clear();
 
   LazyNow lazy_now(real_time_domain()->CreateLazyNow());
-  base::TimeTicks task_start_time;
+  base::TimeTicks task_start_time = base::TimeTicks();

[alph, 2016/08/26 18:24:17]

nit: revert this.

[panicker, 2016/08/26 18:27:57]

Can you clarify why this should be removed?
I think it makes sense to initialize task_start_time to base::TimeTicks()

[alph, 2016/08/26 18:35:11]

The original line does also make it call a default constructor on
task_start_time. You don't need to assign it explicitly.

[panicker, 2016/08/26 19:11:39]

Done.

 
-  if (!delegate_->IsNested() && task_time_tracker_)
+  if (!delegate_->IsNested() && task_time_observers_.might_have_observers())
     task_start_time = lazy_now.Now();
 
   // Pass false and nullptr to UpdateWorkQueues here to prevent waking up a
@@ -228,10 +231,12 @@ void TaskQueueManager::DoWork(base::TimeTicks run_time, bool from_main_thread) {
     }
 
     lazy_now = real_time_domain()->CreateLazyNow();
-    if (!delegate_->IsNested() && task_time_tracker_) {
+    if (!delegate_->IsNested() && task_start_time != base::TimeTicks()) {
       // Only report top level task durations.
       base::TimeTicks task_end_time = lazy_now.Now();
-      task_time_tracker_->ReportTaskTime(task_start_time, task_end_time);
+      FOR_EACH_OBSERVER(TaskTimeObserver, task_time_observers_,
+                        ReportTaskTime(MonotonicTimeInSeconds(task_start_time),
+                                       MonotonicTimeInSeconds(task_end_time)));
       task_start_time = task_end_time;
     }
 
@@ -374,6 +379,17 @@ void TaskQueueManager::RemoveTaskObserver(
   task_observers_.RemoveObserver(task_observer);
 }
 
+void TaskQueueManager::AddTaskTimeObserver(TaskTimeObserver* task_time_observer) {
+  DCHECK(main_thread_checker_.CalledOnValidThread());
+  task_time_observers_.AddObserver(task_time_observer);
+}
+
+void TaskQueueManager::RemoveTaskTimeObserver(
+    TaskTimeObserver* task_time_observer) {
+  DCHECK(main_thread_checker_.CalledOnValidThread());
+  task_time_observers_.RemoveObserver(task_time_observer);
+}
+
 bool TaskQueueManager::GetAndClearSystemIsQuiescentBit() {
   bool task_was_run = task_was_run_on_quiescence_monitored_queue_;
   task_was_run_on_quiescence_monitored_queue_ = false;