content: Add RendererScheduler.

content/renderer/scheduler/renderer_scheduler.h

+// 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.
+
+#ifndef CONTENT_RENDERER_SCHEDULER_RENDERER_SCHEDULER_H_
+#define CONTENT_RENDERER_SCHEDULER_RENDERER_SCHEDULER_H_
+
+#include "base/atomicops.h"
+#include "base/synchronization/lock.h"
+#include "base/task/task_queue_manager.h"
+#include "base/threading/thread_checker.h"
+
+namespace cc {
+struct BeginFrameArgs;
+}
+
+namespace content {
+
+class RendererSchedulerSelector;
+
+class RendererScheduler {
+ public:
+  RendererScheduler();
+  ~RendererScheduler();
+
+  // Returns the default task runner.
+  scoped_refptr<base::SingleThreadTaskRunner> DefaultTaskRunner();

[Sami, 2014/10/22 13:26:06]

These guys could be const, right (now that I fixed the corresponding function in
TQM)?

+
+  // Returns the compositor task runner.
+  scoped_refptr<base::SingleThreadTaskRunner> CompositorTaskRunner();
+
+  // Returns the idle task runner.
+  scoped_refptr<base::SingleThreadTaskRunner> IdleTaskRunner();
+
+  // Called to notify about the start of a new frame.  Must be called from the
+  // main thread.
+  void WillBeginFrame(const cc::BeginFrameArgs& args);

[alexclarke, 2014/10/22 10:06:37]

Perhaps this could post itself onto the kControlTaskQueue if it's called from a
different thread?

[Sami, 2014/10/22 13:26:06]

It should never be called from a different thread so I think we can just assert
that.

+
+  // Called to notify that a previously begun frame was committed. Must be
+  // called from the main thread.
+  void DidCommitFrameToCompositor();

[alexclarke, 2014/10/22 10:06:37]

Likewise perhaps this could post itself onto the kControlTaskQueue if it's
called from a different thread?

[Sami, 2014/10/22 13:26:06]

Likewise. I think we should try to limit things to the use cases we'll actually
encounter.

+
+  // Tells the scheduler that the system received an input event. Can be called
+  // on any thread.
+  void DidReceiveInputEvent();
+
+  // Returns true if there is high priority work pending on the main thread
+  // and the caller should yield to let the scheduler service that work.
+  // Must be called from the main thread.
+  bool ShouldYieldForHighPriorityWork();
+
+  // Returns the deadline by which an idle task should finish by for the
+  // current frame. Must be called from the main thread.
+  base::TimeTicks CurrentFrameDeadlineForIdleTasks() const;
+
+ private:
+  enum QueueId {
+    kDefaultTaskQueue,
+    kCompositorTaskQueue,
+    kIdleTaskQueue,
+    kControlTaskQueue,
+    // Must be the last entry.
+    kTaskQueueCount,
+  };
+
+  enum Policy {
+    kNormalPriorityPolicy,
+    kCompositorPriorityPolicy,
+  };
+
+  // The time we should stay in CompositorPriority mode for after a touch event.
+  static const int kCompositorPriorityAfterTouchMillis = 100;
+
+  // Returns the current scheduler policy. This may involve updating the
+  // current policy if a new signal has arrived. Must be called from the main
+  // thread.
+  Policy SchedulerPolicy();
+
+  // Updates the scheduler policy. Must be called from the main thread.
+  void UpdatePolicy();
+
+  // Start and end an idle period.
+  void StartIdlePeriod();
+  void EndIdlePeriod();
+
+  base::ThreadChecker main_thread_checker_;

[alexclarke, 2014/10/22 10:06:37]

It might make sense to add a struct to gather together all variables that must
only be accessed on a particular thread or inside a the lock.

+  scoped_ptr<RendererSchedulerSelector> renderer_scheduler_selector_;
+  base::TaskQueueManager task_queue_manager_;
+  scoped_refptr<base::SingleThreadTaskRunner> control_task_runner_;
+
+  // Don't access current_policy_ directly, instead use SchedulerPolicy().
+  base::subtle::AtomicWord policy_may_need_update_;
+  Policy current_policy_;
+
+  base::TimeTicks estimated_next_frame_begin_;
+
+  // The incoming_signals_lock_ mutex protects access to last_input_time_.
+  base::Lock incoming_signals_lock_;
+  base::TimeTicks last_input_time_;
+};
+
+}  // namespace content
+
+#endif  // CONTENT_RENDERER_SCHEDULER_RENDERER_SCHEDULER_H_