Introduce a SchedulerHelper in content/child/scheduler

content/child/scheduler/null_idle_task_runner.h

Index: content/child/scheduler/null_idle_task_runner.h
diff --git a/content/common/gpu/media/vp8_picture.h b/content/child/scheduler/null_idle_task_runner.h
similarity index 23%
copy from content/common/gpu/media/vp8_picture.h
copy to content/child/scheduler/null_idle_task_runner.h
index 1187698e7a70ce1c5920b53a0ce101f19ef6a464..31a83fc5098546184ed6860f5f54935145d45efb 100644
--- a/content/common/gpu/media/vp8_picture.h
+++ b/content/child/scheduler/null_idle_task_runner.h
@@ -2,28 +2,34 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-#ifndef CONTENT_COMMON_GPU_MEDIA_VP8_PICTURE_H_
-#define CONTENT_COMMON_GPU_MEDIA_VP8_PICTURE_H_
+#ifndef CONTENT_CHILD_SCHEDULER_NULL_IDLE_TASK_RUNNER_H_
+#define CONTENT_CHILD_SCHEDULER_NULL_IDLE_TASK_RUNNER_H_
 
-#include "base/memory/ref_counted.h"
+#include "content/child/scheduler/single_thread_idle_task_runner.h"
 
 namespace content {
 
-class V4L2VP8Picture;
-
-class VP8Picture : public base::RefCounted<VP8Picture> {
+class NullIdleTaskRunner : public SingleThreadIdleTaskRunner {
  public:
-  VP8Picture();
+  NullIdleTaskRunner();
+  void PostIdleTask(const tracked_objects::Location& from_here,
+                    const IdleTask& idle_task) override;
+
+  void PostNonNestableIdleTask(
+      const tracked_objects::Location& from_here,
+      const IdleTask& idle_task) override;
 
-  virtual V4L2VP8Picture* AsV4L2VP8Picture();
+  void PostIdleTaskAfterWakeup(
+      const tracked_objects::Location& from_here,
+      const IdleTask& idle_task) override;
 
  protected:
-  friend class base::RefCounted<VP8Picture>;
-  virtual ~VP8Picture();
+  ~NullIdleTaskRunner() override;
 
-  DISALLOW_COPY_AND_ASSIGN(VP8Picture);
+ private:
+  DISALLOW_COPY_AND_ASSIGN(NullIdleTaskRunner);
 };
 
 }  // namespace content
 
-#endif  // CONTENT_COMMON_GPU_MEDIA_VP8_PICTURE_H_
+#endif  // CONTENT_CHILD_SCHEDULER_NULL_IDLE_TASK_RUNNER_H_