content: Add RendererScheduler.

content/renderer/scheduler/renderer_scheduler_impl.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_IMPL_H_
+#define CONTENT_RENDERER_SCHEDULER_RENDERER_SCHEDULER_IMPL_H_
+
+#include "base/atomicops.h"
+#include "base/synchronization/lock.h"
+#include "base/threading/thread_checker.h"
+#include "content/renderer/scheduler/renderer_scheduler.h"
+#include "content/renderer/scheduler/single_thread_idle_task_runner.h"
+#include "content/renderer/scheduler/task_queue_manager.h"
+
+namespace content {
+
+class RendererSchedulerSelector;
+
+class RendererSchedulerImpl : public RendererScheduler,
+                              private IdleTaskDeadlineSupplier {
+ public:
+  RendererSchedulerImpl();
+  virtual ~RendererSchedulerImpl();
+
+  // Returns the default task runner.
+  scoped_refptr<base::SingleThreadTaskRunner> DefaultTaskRunner() override;
+
+  // Returns the compositor task runner.
+  scoped_refptr<base::SingleThreadTaskRunner> CompositorTaskRunner() override;
+
+  // Returns the idle task runner. Tasks posted to this runner may be reordered
+  // relative to other task types and may be starved for an arbitrarily long
+  // time if no idle time is available.
+  scoped_refptr<SingleThreadIdleTaskRunner> IdleTaskRunner() override;
+
+  // Called to notify about the start of a new frame.  Must be called from the
+  // main thread.
+  void WillBeginFrame(const cc::BeginFrameArgs& args) override;
+
+  // Called to notify that a previously begun frame was committed. Must be
+  // called from the main thread.
+  void DidCommitFrameToCompositor() override;
+
+  // Tells the scheduler that the system received an input event. Can be called
+  // on any thread.
+  void DidReceiveInputEvent() override;
+
+  // 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() override;
+
+ protected:
+  RendererSchedulerImpl(
+      scoped_refptr<base::SingleThreadTaskRunner> main_task_runner);
+
+  // Virtual for testing.
+  virtual base::TimeTicks Now() const;
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(RendererSchedulerImpl);
+  friend base::WeakPtr<content::IdleTaskDeadlineSupplier>;
+  friend class RendererSchedulerImplTest;
+
+  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;
+
+  // Implementation of IdleTaskDeadlineSupplier
+  virtual base::TimeTicks CurrentIdleTaskDeadline() const override;
+
+  // 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();
+
+  // Posts a call to UpdatePolicy on the control runner to be run after |delay|
+  void PostUpdatePolicyOnControlRunner(base::TimeDelta delay);
+
+  // 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, 2014/10/24 15:56:30]

I think it might be useful to group these by which thread they're allowed to be
accessed from.

[rmcilroy, 2014/10/27 16:25:01]

It's not easy to do this and still maintain constructor initialization order
(e.g., the weak_factory needs to be at the end in order to work correctly). 
Done as best as I can

+  scoped_ptr<RendererSchedulerSelector> renderer_scheduler_selector_;
+  TaskQueueManager task_queue_manager_;
+  scoped_refptr<base::SingleThreadTaskRunner> control_task_runner_;
+  scoped_refptr<SingleThreadIdleTaskRunner> idle_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_
+  // and write access to policy_may_need_update_.
+  base::Lock incoming_signals_lock_;
+  base::TimeTicks last_input_time_;
+
+  base::WeakPtr<RendererSchedulerImpl> weak_renderer_scheduler_ptr_;
+  base::WeakPtrFactory<RendererSchedulerImpl> weak_factory_;
+};
+
+}  // namespace content
+
+#endif  // CONTENT_RENDERER_SCHEDULER_RENDERER_SCHEDULER_IMPL_H_