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/threading/thread_checker.h"

[no sievers, 2014/11/04 20:41:41]

nit: are the top 3 includes not needed?

[rmcilroy, 2014/11/05 00:34:00]

Done

+#include "content/renderer/scheduler/single_thread_idle_task_runner.h"
+#include "content/renderer/scheduler/task_queue_manager.h"
+
+namespace cc {
+struct BeginFrameArgs;
+}
+
+namespace content {
+
+class CONTENT_EXPORT RendererScheduler {
+ public:
+  virtual ~RendererScheduler();
+  static scoped_ptr<RendererScheduler> Create();
+
+  // Returns the default task runner.
+  virtual scoped_refptr<base::SingleThreadTaskRunner> DefaultTaskRunner() = 0;
+
+  // Returns the compositor task runner.
+  virtual scoped_refptr<base::SingleThreadTaskRunner>
+  CompositorTaskRunner() = 0;
+
+  // 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.
+  virtual scoped_refptr<SingleThreadIdleTaskRunner> IdleTaskRunner() = 0;
+
+  // Called to notify about the start of a new frame.  Must be called from the
+  // main thread.
+  virtual void WillBeginFrame(const cc::BeginFrameArgs& args) = 0;
+
+  // Called to notify that a previously begun frame was committed. Must be
+  // called from the main thread.
+  virtual void DidCommitFrameToCompositor() = 0;
+
+  // Tells the scheduler that the system received an input event. Can be called
+  // on any thread.
+  virtual void DidReceiveInputEvent() = 0;

[no sievers, 2014/11/04 20:41:41]

Should this maybe just be called DidReceiveInputEventOnCompositorThread() to
make things really clear?
Especially since it's the only member function that's called on another thread.

[rmcilroy, 2014/11/05 00:34:00]

Done.

+
+  // 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.
+  virtual bool ShouldYieldForHighPriorityWork() = 0;
+
+  // Shuts down the scheduler by draining any remaining pending work in the work

[no sievers, 2014/11/04 20:41:41]

Is the 'draining' part true? Doesn't look like that would happen during a call
to ShutDown() if at all.

[rmcilroy, 2014/11/05 00:34:00]

By deleting the task_queue_manager this means that the remaining tasks in the
task queues are also deleted and won't be run after this point.  This is what I
mean by draining the queue (i.e., they get dropped) - is this clear or would you
like me to reword the comment to make it clearer what exactly happens here?

[no sievers, 2014/11/05 21:18:57]

I'd change it to say that it's dropping/discarding any pending tasks then.
Draining sounds a bit like they get run synchronously here.

[rmcilroy, 2014/11/05 22:40:34]

Done.

+  // queues.
+  virtual void Shutdown() = 0;
+
+ protected:
+  RendererScheduler();
+  DISALLOW_COPY_AND_ASSIGN(RendererScheduler);
+};
+
+}  // namespace content
+
+#endif  // CONTENT_RENDERER_SCHEDULER_RENDERER_SCHEDULER_H_