Record PendingTaskCount when a backgrounded renderer is suspended.

third_party/WebKit/Source/platform/scheduler/child/idle_helper.cc

Index: third_party/WebKit/Source/platform/scheduler/child/idle_helper.cc
diff --git a/third_party/WebKit/Source/platform/scheduler/child/idle_helper.cc b/third_party/WebKit/Source/platform/scheduler/child/idle_helper.cc
index 8f934aaf9b77fba8020dc99a713e77d1b1cdebae..61772a7e5ec01f287012bd6c5b8d4e3137c60b73 100644
--- a/third_party/WebKit/Source/platform/scheduler/child/idle_helper.cc
+++ b/third_party/WebKit/Source/platform/scheduler/child/idle_helper.cc
@@ -472,5 +472,9 @@ const char* IdleHelper::IdlePeriodStateToString(
   }
 }
 
+int IdleHelper::GetNumberOfPendingIdleTasks() {
+  return idle_queue_->GetNumberOfPendingTasks();
+}
+
 }  // namespace scheduler
 }  // namespace blink