Record PendingTaskCount when a backgrounded renderer is suspended.

third_party/WebKit/Source/platform/scheduler/base/task_queue_manager.cc

Index: third_party/WebKit/Source/platform/scheduler/base/task_queue_manager.cc
diff --git a/third_party/WebKit/Source/platform/scheduler/base/task_queue_manager.cc b/third_party/WebKit/Source/platform/scheduler/base/task_queue_manager.cc
index 7def64ac93093b72ead7c15b75b697fc0de71f4e..e508d0229a72f6e6be9549ef1307fce02d4a0570 100644
--- a/third_party/WebKit/Source/platform/scheduler/base/task_queue_manager.cc
+++ b/third_party/WebKit/Source/platform/scheduler/base/task_queue_manager.cc
@@ -426,6 +426,13 @@ LazyNow TaskQueueManager::CreateLazyNow() const {
   return LazyNow(delegate_.get());
 }
 
+size_t TaskQueueManager::GetNumberOfPendingTasks() const {
+  size_t task_count = 0;
+  for (auto& queue : queues_)
+    task_count += queue->GetNumberOfPendingTasks();
+  return task_count;
+}
+
 std::unique_ptr<base::trace_event::ConvertableToTraceFormat>
 TaskQueueManager::AsValueWithSelectorResult(
     bool should_run,