TaskScheduler: Add TRACE_TASK_EXECUTION to TaskTracker::RunTask.

base/task_scheduler/task_tracker.cc

Index: base/task_scheduler/task_tracker.cc
diff --git a/base/task_scheduler/task_tracker.cc b/base/task_scheduler/task_tracker.cc
index 29951a60f4b51020142ffb8fe32f2860b1af1a3d..460fa519435dc48f61574301c53cc5f0114ed2fc 100644
--- a/base/task_scheduler/task_tracker.cc
+++ b/base/task_scheduler/task_tracker.cc
@@ -8,6 +8,7 @@
 #include "base/debug/task_annotator.h"
 #include "base/metrics/histogram_macros.h"
 #include "base/threading/thread_restrictions.h"
+#include "base/trace_event/trace_event.h"
 
 namespace base {
 namespace internal {
@@ -15,6 +16,7 @@ namespace internal {
 namespace {
 
 const char kQueueFunctionName[] = "base::PostTask";
+const char kRunFunctionName[] = "base::RunTask";

[fdoray, 2016/05/02 19:50:08]

I don't want to call this TaskTracker::RunTask because TaskTracker is an
implementation detail of the task scheduler.

[gab, 2016/05/02 20:31:22]

Okay but base::RunTask isn't a thing... Maybe just "TaskSchedulerRunTask"? At
least not making it look like a base:: method.

[fdoray, 2016/05/03 14:06:36]

Done.

 
 // Upper bound for the
 // TaskScheduler.BlockShutdownTasksPostedDuringShutdown histogram.
@@ -79,6 +81,8 @@ void TaskTracker::RunTask(const Task* task) {
   if (!BeforeRunTask(shutdown_behavior))
     return;
 
+  TRACE_TASK_EXECUTION(kRunFunctionName, *task);

[gab, 2016/05/02 20:31:22]

https://codereview.chromium.org/1911023002/ is scoping line 94's RunTask, this
should probably go in there (or is it using a singleton and forced to be above
the SetSingletonAllowed call?)

[robliao, 2016/05/02 20:32:34]

Should this occur right after we SetSingletonAllowed?

[fdoray, 2016/05/03 14:06:36]

I initially included SetSingletonAllowed into TRACE_TASK_EXECUTION's scope
because it usually includes a little bit more than the task execution itself
[1][2][3]. Not sure we really want that though so the scope now includes the
task execution only.

[1]
https://code.google.com/p/chromium/codesearch#chromium/src/base/message_loop/...
[2]
https://code.google.com/p/chromium/codesearch#chromium/src/base/threading/wor...
[3]
https://code.google.com/p/chromium/codesearch#chromium/src/components/schedul...

+
   // All tasks run through here and the scheduler itself doesn't use singletons.
   // Therefore, it isn't necessary to reset the singleton allowed bit after
   // running the task.