Report expected task queueing time via UMA

components/scheduler/child/scheduler_helper.h

Index: components/scheduler/child/scheduler_helper.h
diff --git a/components/scheduler/child/scheduler_helper.h b/components/scheduler/child/scheduler_helper.h
index 0348a6808792118a742870a57642af06e0a85b03..879e8c18fa4c84db84ca73de1821d29610f41f8c 100644
--- a/components/scheduler/child/scheduler_helper.h
+++ b/components/scheduler/child/scheduler_helper.h
@@ -11,6 +11,7 @@
 #include "base/time/tick_clock.h"
 #include "components/scheduler/base/task_queue_manager.h"
 #include "components/scheduler/base/task_queue_selector.h"
+#include "components/scheduler/base/task_time_tracker.h"
 #include "components/scheduler/scheduler_export.h"
 
 namespace base {
@@ -22,7 +23,9 @@ namespace scheduler {
 class SchedulerTqmDelegate;
 
 // Common scheduler functionality for default tasks.
-class SCHEDULER_EXPORT SchedulerHelper : public TaskQueueManager::Observer {
+class SCHEDULER_EXPORT SchedulerHelper
+    : public TaskQueueManager::Observer,
+      public TaskTimeTracker::TaskTimeObserver {
  public:
   // Category strings must have application lifetime (statics or
   // literals). They may not include " chars.
@@ -38,6 +41,9 @@ class SCHEDULER_EXPORT SchedulerHelper : public TaskQueueManager::Observer {
   void OnTriedToExecuteBlockedTask(const TaskQueue& queue,
                                    const base::PendingTask& task) override;
 
+  // TaskTimeTracker::TaskTimeObserver implementation:
+  void OnQueueingTimeForWindowEstimated(base::TimeDelta queueing_time) override;
+
   // Returns the default task runner.
   scoped_refptr<TaskQueue> DefaultTaskRunner();
 
@@ -108,6 +114,7 @@ class SCHEDULER_EXPORT SchedulerHelper : public TaskQueueManager::Observer {
 
   base::ThreadChecker thread_checker_;
   scoped_refptr<SchedulerTqmDelegate> task_queue_manager_delegate_;
+  TaskTimeTracker task_time_tracker_;

[alex clarke (OOO till 29th), 2016/07/05 13:47:45]

The patch might be a bit smaller if this was moved into the TQM.  The
SchedulerHelper is a bit of a vestigial class from earlier incarnations of the
Scheduler that Sami and I have occasionally talked about getting rid of.

Sami WDYT?

[tdresser, 2016/07/05 14:30:13]

Shubhie said via email:
"I put the TaskTimeTracker in the SchedulerHelper so that I can query it from
RendererSchedulerImpl as part of the usual plumbing drill for WebWidget (example
my previous CL)"

I don't think the ownership matters either way, I can move that if you want, but
we're still going to need a reference to it from the SchedulerHelper, as far as
I know.

   std::unique_ptr<TaskQueueManager> task_queue_manager_;
   scoped_refptr<TaskQueue> control_task_runner_;
   scoped_refptr<TaskQueue> control_after_wakeup_task_runner_;