[content] Add support for Non nestable idle tasks the the RendererScheduler

content/renderer/scheduler/nestable_single_thread_task_runner.h

+// Copyright 2015 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.
+
+#ifndef CONTENT_RENDERER_SCHEDULER_NESTABLE_SINGLE_THREAD_TASK_RUNNER_H_
+#define CONTENT_RENDERER_SCHEDULER_NESTABLE_SINGLE_THREAD_TASK_RUNNER_H_
+
+#include "base/single_thread_task_runner.h"
+#include "content/common/content_export.h"
+
+namespace content {
+
+// A single thread task runner which exposes whether it is running nested.
+class CONTENT_EXPORT NestableSingleThreadTaskRunner
+    : public base::SingleThreadTaskRunner {
+ public:
+  NestableSingleThreadTaskRunner() {}
+
+  // Returns true if the task runner is nested (i.e., running a run loop within
+  // a nested task).
+  virtual bool IsNested() const = 0;
+
+ protected:
+  ~NestableSingleThreadTaskRunner() override {}
+
+  DISALLOW_COPY_AND_ASSIGN(NestableSingleThreadTaskRunner);
+};
+
+}  // namespace content
+
+#endif  // CONTENT_RENDERER_SCHEDULER_NESTABLE_SINGLE_THREAD_TASK_RUNNER_H_