Update flow events tracing in SequencedWorkerPool::Inner::PostTask an…

…d SequencedWorkerPool::Inner::ThreadLoop to use Flow v2.

BUG=catapult-project/catapult#1079

Review URL: https://codereview.chromium.org/1296463004

Cr-Commit-Position: refs/heads/master@{#344055}

base/threading/sequenced_worker_pool.cc

@@ -619,9 +619,10 @@ bool SequencedWorkerPool::Inner::PostTask(
     // The trace_id is used for identifying the task in about:tracing.
     sequenced.trace_id = trace_id_++;
 
-    TRACE_EVENT_FLOW_BEGIN0(TRACE_DISABLED_BY_DEFAULT("toplevel.flow"),
-        "SequencedWorkerPool::PostTask",
-        TRACE_ID_MANGLE(GetTaskTraceID(sequenced, static_cast<void*>(this))));
+    TRACE_EVENT_WITH_FLOW0(TRACE_DISABLED_BY_DEFAULT("toplevel.flow"),
+        "SequencedWorkerPool::Inner::PostTask",
+        TRACE_ID_MANGLE(GetTaskTraceID(sequenced, static_cast<void*>(this))),
+        TRACE_EVENT_FLAG_FLOW_OUT);
 
     sequenced.sequence_task_number = LockedGetNextSequenceTaskNumber();
 
@@ -754,12 +755,12 @@ void SequencedWorkerPool::Inner::ThreadLoop(Worker* this_worker) {
       GetWorkStatus status =
           GetWork(&task, &wait_time, &delete_these_outside_lock);
       if (status == GET_WORK_FOUND) {
-        TRACE_EVENT_FLOW_END0(TRACE_DISABLED_BY_DEFAULT("toplevel.flow"),
-            "SequencedWorkerPool::PostTask",
-            TRACE_ID_MANGLE(GetTaskTraceID(task, static_cast<void*>(this))));
-        TRACE_EVENT2("toplevel", "SequencedWorkerPool::ThreadLoop",
-                     "src_file", task.posted_from.file_name(),
-                     "src_func", task.posted_from.function_name());
+        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());
         int new_thread_id = WillRunWorkerTask(task);
         {
           AutoUnlock unlock(lock_);