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 RendererTaskQueueSelector;
+
+class RendererSchedulerImpl : public RendererScheduler,
+                              private IdleTaskDeadlineSupplier {
+ public:
+  RendererSchedulerImpl();

[no sievers, 2014/10/30 23:40:51]

is this constructor needed?

[rmcilroy, 2014/11/03 19:02:52]

Good point, replaced it with the previously protected one.

+  ~RendererSchedulerImpl() override;

[no sievers, 2014/10/30 23:40:51]

nit: can this be protected?

[rmcilroy, 2014/11/03 19:02:52]

Unfortunately not since we wrap it in a scoped_ptr

+
+  // RendererScheduler implementation:
+  scoped_refptr<base::SingleThreadTaskRunner> DefaultTaskRunner() override;
+  scoped_refptr<base::SingleThreadTaskRunner> CompositorTaskRunner() override;
+  scoped_refptr<SingleThreadIdleTaskRunner> IdleTaskRunner() override;
+  void WillBeginFrame(const cc::BeginFrameArgs& args) override;
+  void DidCommitFrameToCompositor() override;
+  void DidReceiveInputEvent() override;
+  bool ShouldYieldForHighPriorityWork() override;
+  void Shutdown() override;
+
+ protected:
+  RendererSchedulerImpl(
+      scoped_refptr<base::SingleThreadTaskRunner> main_task_runner);
+
+  // Virtual for testing.
+  virtual base::TimeTicks Now() const;
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(RendererSchedulerImpl);

[no sievers, 2014/10/30 23:40:51]

nit: make this the last thing in the class (style-guide)

[rmcilroy, 2014/11/03 19:02:52]

Done.

+  friend base::WeakPtr<content::IdleTaskDeadlineSupplier>;
+  friend class RendererSchedulerImplTest;
+
+  enum QueueId {
+    DEFAULT_TASK_QUEUE,
+    COMPOSITOR_TASK_QUEUE,
+    IDLE_TASK_QUEUE,
+    CONTROL_TASK_QUEUE,
+    // Must be the last entry.
+    TASK_QUEUE_COUNT,
+  };
+
+  enum Policy {
+    NORMAL_PRIORITY_POLICY,
+    COMPOSITOR_PRIORITY_POLICY,
+  };
+
+  // The time we should stay in CompositorPriority mode for after a touch event.
+  static const int kCompositorPriorityAfterTouchMillis = 100;

[no sievers, 2014/10/30 23:40:51]

So this covers multiple frames. So we are basically always in compositor prio
mode while there is some sort of touch interaction going on?

[alex clarke (OOO till 29th), 2014/11/03 17:39:34]

Yes the idea is we want smooth and responsive scrolling while the user is
touching or during a fling.  The 100ms duration is a number I pulled out of thin
air, but it seems to behave reasonably.

[rmcilroy, 2014/11/03 19:02:52]

Yes that is the idea, we try to stay in compositor mode while touch events are
going on.

+
+  // IdleTaskDeadlineSupplier Implementation:
+  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_;
+  scoped_ptr<RendererTaskQueueSelector> renderer_task_queue_selector_;
+  scoped_ptr<TaskQueueManager> task_queue_manager_;
+  scoped_refptr<base::SingleThreadTaskRunner> control_task_runner_;
+  scoped_refptr<base::SingleThreadTaskRunner> default_task_runner_;
+  scoped_refptr<base::SingleThreadTaskRunner> compositor_task_runner_;
+  scoped_refptr<SingleThreadIdleTaskRunner> idle_task_runner_;
+
+  // Don't access current_policy_ directly, instead use SchedulerPolicy().
+  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::subtle::AtomicWord policy_may_need_update_;
+
+  base::WeakPtr<RendererSchedulerImpl> weak_renderer_scheduler_ptr_;
+  base::WeakPtrFactory<RendererSchedulerImpl> weak_factory_;
+};
+
+}  // namespace content
+
+#endif  // CONTENT_RENDERER_SCHEDULER_RENDERER_SCHEDULER_IMPL_H_