Expected Queueing Time Metric ignores tasks with nested message loops.

third_party/WebKit/Source/platform/scheduler/renderer/renderer_scheduler_impl.cc

 // Copyright 2014 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 "platform/scheduler/renderer/renderer_scheduler_impl.h"
 
 #include "base/bind.h"
 #include "base/debug/stack_trace.h"
 #include "base/logging.h"
 #include "base/memory/ptr_util.h"
@@ skipping 1767 matching lines @@
       start_time_ticks, end_time_ticks);
   // TODO(altimin): Per-page metrics should also be considered.
   UMA_HISTOGRAM_CUSTOM_COUNTS(
       "RendererScheduler.TaskTime",
       (end_time_ticks - start_time_ticks).InMicroseconds(), 1, 1000000, 50);
   UMA_HISTOGRAM_ENUMERATION("RendererScheduler.NumberOfTasksPerQueueType",
                             static_cast<int>(task_queue->GetQueueType()),
                             static_cast<int>(TaskQueue::QueueType::COUNT));
 }
 
+void RendererSchedulerImpl::onBeginNestedMessageLoop() {
+  seqlock_queueing_time_estimator_.seqlock.WriteBegin();
+  seqlock_queueing_time_estimator_.data.OnBeginNestedMessageLoop();
+  seqlock_queueing_time_estimator_.seqlock.WriteEnd();
+}
+
 void RendererSchedulerImpl::AddTaskTimeObserver(
     TaskTimeObserver* task_time_observer) {
   helper_.AddTaskTimeObserver(task_time_observer);
 }
 
 void RendererSchedulerImpl::RemoveTaskTimeObserver(
     TaskTimeObserver* task_time_observer) {
   helper_.RemoveTaskTimeObserver(task_time_observer);
 }
 
@@ skipping 115 matching lines @@
     case TimeDomainType::VIRTUAL:
       return "virtual";
     default:
       NOTREACHED();
       return nullptr;
   }
 }
 
 }  // namespace scheduler
 }  // namespace blink