CC: Add 'cc-benchmark' traces for minimal tracing in benchmarks.

base/threading/sequenced_worker_pool.cc

Index: base/threading/sequenced_worker_pool.cc
diff --git a/base/threading/sequenced_worker_pool.cc b/base/threading/sequenced_worker_pool.cc
index 813005cc07106e8b53da3d604e4e648354d51d14..da4f63d6996b29f5d79da2d39df5b60c57cbdb5d 100644
--- a/base/threading/sequenced_worker_pool.cc
+++ b/base/threading/sequenced_worker_pool.cc
@@ -593,7 +593,7 @@ 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"),
+    TRACE_EVENT_FLOW_BEGIN0(TRACE_DISABLED_BY_DEFAULT("task.flow"),
         "SequencedWorkerPool::PostTask",
         TRACE_ID_MANGLE(GetTaskTraceID(sequenced, static_cast<void*>(this))));
 
@@ -727,10 +727,10 @@ 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"),
+        TRACE_EVENT_FLOW_END0(TRACE_DISABLED_BY_DEFAULT("task.flow"),
             "SequencedWorkerPool::PostTask",
             TRACE_ID_MANGLE(GetTaskTraceID(task, static_cast<void*>(this))));
-        TRACE_EVENT2("toplevel", "SequencedWorkerPool::ThreadLoop",
+        TRACE_EVENT2("task", "SequencedWorkerPool::ThreadLoop",
                      "src_file", task.posted_from.file_name(),
                      "src_func", task.posted_from.function_name());
         int new_thread_id = WillRunWorkerTask(task);