Add a |scope| argument to TRACE_EVENT_INSTANT* and require its presence.

cc/base/worker_pool.cc

 // Copyright 2013 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 "cc/base/worker_pool.h"
 
 #include "base/bind.h"
 #include "base/debug/trace_event.h"
 #include "base/stringprintf.h"
 #include "base/synchronization/condition_variable.h"
@@ skipping 531 matching lines @@
   while (true) {
     base::TimeTicks time_limit = run_cheap_tasks_time_limit_;
 
     if (!check_for_completed_tasks_time_.is_null())
       time_limit = std::min(time_limit, check_for_completed_tasks_time_);
 
     bool is_idle = inner_->RunCheapTasksUntilTimeLimit(time_limit);
 
     base::TimeTicks now = base::TimeTicks::Now();
     if (now >= run_cheap_tasks_time_limit_) {
-      TRACE_EVENT_INSTANT0("cc", "WorkerPool::RunCheapTasks out of time");
+      TRACE_EVENT_INSTANT0("cc", "WorkerPool::RunCheapTasks out of time",
+                           TRACE_EVENT_SCOPE_THREAD);
       break;
     }
 
     // We must be out of cheap tasks if this happens.
     if (check_for_completed_tasks_time_.is_null() ||
         now < check_for_completed_tasks_time_)
       break;
 
-    TRACE_EVENT_INSTANT0("cc", "WorkerPool::RunCheapTasks check time");
+    TRACE_EVENT_INSTANT0("cc", "WorkerPool::RunCheapTasks check time",
+                         TRACE_EVENT_SCOPE_THREAD);
     CancelCheckForCompletedTasks();
     DispatchCompletionCallbacks();
     // Schedule another check for completed tasks if not idle.
     if (!is_idle)
       ScheduleCheckForCompletedTasks();
   }
 }
 
 }  // namespace cc