[scheduler] Removing unnecessary trace event tracking multiple tasks.

The trace event spanning multiple tasks is no longer used and can be removed.

This cl also changes the name of the task trace event in ThreadControllerWithMessagePumpImpl
to match the task trace event in ThreadControllerImpl.

Bug: 980697
Change-Id: I1c3dbc31e64cb7cbd5d87e1c6336775230d4a80a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1688338
Commit-Queue: Katie Dillon <kdillon@chromium.org>
Reviewed-by: Alexander Timin <altimin@chromium.org>
Reviewed-by: Timothy Dresser <tdresser@chromium.org>
Cr-Commit-Position: refs/heads/master@{#675797}

base/task/sequence_manager/thread_controller_impl.cc

@@ -163,7 +163,8 @@ void ThreadControllerImpl::WillQueueTask(PendingTask* pending_task,
 }
 
 void ThreadControllerImpl::DoWork(WorkType work_type) {
-  TRACE_EVENT0("sequence_manager", "ThreadControllerImpl::DoWork");
+  TRACE_EVENT0(TRACE_DISABLED_BY_DEFAULT("sequence_manager"),
+               "ThreadControllerImpl::DoWork");
 
   DCHECK_CALLED_ON_VALID_SEQUENCE(associated_thread_->sequence_checker);
   DCHECK(sequence_);

base/task/sequence_manager/thread_controller_with_message_pump_impl.cc

@@ -330,18 +330,15 @@ bool ThreadControllerWithMessagePumpImpl::DoDelayedWork(
 TimeDelta ThreadControllerWithMessagePumpImpl::DoWorkImpl(
     LazyNow* continuation_lazy_now,
     bool* ran_task) {
+  TRACE_EVENT0(TRACE_DISABLED_BY_DEFAULT("sequence_manager"),
+               "ThreadControllerImpl::DoWork");
+
   if (!main_thread_only().task_execution_allowed) {
     if (main_thread_only().quit_runloop_after == TimeTicks::Max())
       return TimeDelta::Max();
     return main_thread_only().quit_runloop_after - continuation_lazy_now->Now();
   }
 
-  // Keep this in-sync with
-  // third_party/catapult/tracing/tracing/extras/chrome/event_finder_utils.html
-  // TODO(alexclarke): Rename this event to whatever we end up calling this
-  // after the DoWork / DoDelayed work merge.
-  TRACE_EVENT0("toplevel", "ThreadControllerImpl::RunTask");
-
   DCHECK(main_thread_only().task_source);
 
   for (int i = 0; i < main_thread_only().work_batch_size; i++) {
@@ -364,8 +361,8 @@ TimeDelta ThreadControllerWithMessagePumpImpl::DoWorkImpl(
     {
       // Trace events should finish before we call DidRunTask to ensure that
       // SequenceManager trace events do not interfere with them.
-      TRACE_TASK_EXECUTION("ThreadController::Task", *task);
-      task_annotator_.RunTask("ThreadController::Task", &*task);
+      TRACE_TASK_EXECUTION("ThreadControllerImpl::RunTask", *task);
+      task_annotator_.RunTask("SequenceManager RunTask", &*task);
     }
 
 #if DCHECK_IS_ON()