[tracing] Add task execution event for sequenced worker pool

base/threading/sequenced_worker_pool.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "base/threading/sequenced_worker_pool.h"
 
 #include <stdint.h>
 
 #include <list>
 #include <map>
@@ skipping 792 matching lines @@
       std::vector<Closure> delete_these_outside_lock;
       GetWorkStatus status =
           GetWork(&task, &wait_time, &delete_these_outside_lock);
       if (status == GET_WORK_FOUND) {
         TRACE_EVENT_WITH_FLOW2(TRACE_DISABLED_BY_DEFAULT("toplevel.flow"),
             "SequencedWorkerPool::Inner::ThreadLoop",
             TRACE_ID_MANGLE(GetTaskTraceID(task, static_cast<void*>(this))),
             TRACE_EVENT_FLAG_FLOW_IN,
             "src_file", task.posted_from.file_name(),
             "src_func", task.posted_from.function_name());
+        TRACE_EVENT_API_SCOPED_TASK_EXECUTION_EVENT INTERNAL_TRACE_EVENT_UID(

[Primiano Tucci (use gerrit), 2016/05/04 08:21:50]

you don't need EVENT INTERNAL_TRACE_EVENT_UID here.
1) as the name suggests it's internal :)
2) That is only used to disambiguate the local variable name when using the
TRACE_TASK_EXECUTION macro. Since here you are instantiating explicitly you can
just pick a name, e.g.
:

TRACE_EVENT_API_SCOPED_TASK_EXECUTION_EVENT
task_event(task.posted_from.file_name());

[ssid, 2016/05/06 03:15:26]

I added this because every time i didn't in past you had told me to add. yes it
is not required for this case. Sorry.

[Primiano Tucci (use gerrit), 2016/05/06 10:22:03]

Oops. I hope I didn't suggest in non-tracing code, that should be internal and
used only in macros.

+            task_event)(task.posted_from.file_name());
         int new_thread_id = WillRunWorkerTask(task);
         {
           AutoUnlock unlock(lock_);
           // There may be more work available, so wake up another
           // worker thread. (Technically not required, since we
           // already get a signal for each new task, but it doesn't
           // hurt.)
           SignalHasWork();
           delete_these_outside_lock.clear();
 
@@ skipping 573 matching lines @@
 void SequencedWorkerPool::Shutdown(int max_new_blocking_tasks_after_shutdown) {
   DCHECK(constructor_task_runner_->BelongsToCurrentThread());
   inner_->Shutdown(max_new_blocking_tasks_after_shutdown);
 }
 
 bool SequencedWorkerPool::IsShutdownInProgress() {
   return inner_->IsShutdownInProgress();
 }
 
 }  // namespace base