Re-land extract state management from WebMediaPlayerImpl.

media/filters/pipeline_controller.h

+// Copyright 2016 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 MEDIA_FILTERS_PIPELINE_CONTROLLER_H_
+#define MEDIA_FILTERS_PIPELINE_CONTROLLER_H_
+
+#include "base/callback.h"
+#include "base/macros.h"
+#include "base/memory/weak_ptr.h"
+#include "base/time/time.h"
+#include "media/base/media_export.h"
+#include "media/base/pipeline.h"
+#include "media/base/renderer.h"
+
+namespace media {
+
+class ChunkDemuxer;
+class Demuxer;
+
+// PipelineController wraps a Pipeline to expose the one-at-a-time operations
+// (Seek(), Suspend(), and Resume()) with a simpler API. Internally it tracks
+// pending operations and dispatches them when possible. Duplicate requests
+// (such as seeking twice to the same time) may be elided.
+//
+// TODO(sandersd):
+//   - Expose an operation that restarts via suspend+resume.
+//   - Block invalid calls after an error occurs.
+class MEDIA_EXPORT PipelineController
+    : public base::SupportsWeakPtr<PipelineController> {

[DaleCurtis, 2016/02/25 01:58:30]

Do we need SupportsWeakPtr() here? Can you instead use a WeakFactory. I don't
see external classes using this functionality.

[sandersd (OOO until July 31), 2016/02/25 20:33:46]

Done.

+ public:
+  enum class State {
+    CREATED,
+    STARTING,
+    PLAYING,
+    SEEKING,
+    SUSPENDING,
+    SUSPENDED,
+    RESUMING,
+  };
+
+  typedef base::Callback<scoped_ptr<Renderer>(void)> RendererFactoryCB;

[DaleCurtis, 2016/02/25 01:58:30]

"using" instead of typedef now

[sandersd (OOO until July 31), 2016/02/25 20:33:46]

Done.

+  typedef base::Callback<void(bool time_updated)> SeekedCB;
+  typedef base::Callback<void()> SuspendedCB;
+
+  PipelineController(Pipeline* pipeline,

[DaleCurtis, 2016/02/25 01:58:30]

Needs comments about lifetime of pipeline and what each cb does.

[sandersd (OOO until July 31), 2016/02/25 20:33:46]

Those comments made somewhat more sense on the member variables, it's a lot to
take in to document the entire class for the constructor. So what I've done now
is just a summary here.

+                     const RendererFactoryCB& renderer_factory_cb,
+                     const SeekedCB& seeked_cb,
+                     const SuspendedCB& suspended_cb,
+                     const PipelineStatusCB& error_cb);
+  ~PipelineController();
+
+  // Start |pipeline_|. If provided, |chunk_demuxer| will be stored and
+  // StartWaitingForSeek()/CancelPendingSeek() will be issued to it as
+  // necessary. When |is_streaming| is true, Resume() will always start at the
+  // beginning of the stream, rather than attempting to seek to the current
+  // time. Other parameters are just passed directly to pipeline_.Start().
+  void Start(ChunkDemuxer* chunk_demuxer,
+             Demuxer* demuxer,
+             bool is_streaming,
+             const base::Closure& ended_cb,
+             const PipelineMetadataCB& metadata_cb,
+             const BufferingStateCB& buffering_state_cb,
+             const base::Closure& duration_change_cb,
+             const AddTextTrackCB& add_text_track_cb,
+             const base::Closure& waiting_for_decryption_key_cb);
+
+  void Seek(base::TimeDelta time, bool time_updated);

[DaleCurtis, 2016/02/25 01:58:30]

Ditto for comments.

[sandersd (OOO until July 31), 2016/02/25 20:33:46]

Done.

+  void Suspend();
+  void Resume();
+
+  // Returns true if the current state is stable. This means that |state_| is
+  // PLAYING and there are no pending operations. Requests are processed
+  // immediately when the state is stable, otherwise they are queued.
+  // (Exception: Resume() is processed immediately while suspended.)
+  bool IsStable();
+
+  // Returns true if |pipeline_| is suspended.
+  bool IsSuspended();
+
+ private:
+  // Attempts to make progress from the current state to the target state.
+  void Dispatch();
+
+  // PipelineStaus callback that also carries the target state.
+  void OnPipelineStatus(State state, PipelineStatus pipeline_status);
+
+  // The Pipeline we are managing state for.
+  Pipeline* pipeline_ = nullptr;
+
+  // Factory for Renderers, used for Start() and Resume().
+  RendererFactoryCB renderer_factory_cb_;
+
+  // Called after seeks (which includes Start()) upon reaching a stable state.
+  // Multiple seeks result in only one callback if no stable state occurs
+  // between them.
+  SeekedCB seeked_cb_;
+
+  // Called immediately when |pipeline_| completes a suspend operation.
+  SuspendedCB suspended_cb_;
+
+  // Called immediately when any operation on |pipeline_| results in an error.
+  PipelineStatusCB error_cb_;
+
+  // State for handling StartWaitingForSeek()/CancelPendingSeek().
+  ChunkDemuxer* chunk_demuxer_ = nullptr;
+  bool waiting_for_seek_ = false;
+
+  // When true, Resume() will start at time zero instead of seeking to the
+  // current time.
+  bool is_streaming_ = false;
+
+  // Tracks the current state of |pipeline_|.
+  State state_ = State::CREATED;
+
+  // Indicates that a seek has occurred. When set, a seeked callback will be
+  // issued at the next stable state.
+  bool pending_seeked_ = false;
+
+  // Indicates that time has been changed by a seek, which will be reported at
+  // the next seeked callback.
+  bool pending_time_update_ = false;
+
+  // The target time of the active seek; valid while SEEKING or RESUMING.
+  base::TimeDelta seek_time_;
+
+  // Target state which we will work to achieve. |pending_seek_time_| is only
+  // valid when |pending_seek_| is true.
+  bool pending_seek_ = false;
+  base::TimeDelta pending_seek_time_;
+  bool pending_suspend_ = false;
+  bool pending_resume_ = false;
+
+  DISALLOW_COPY_AND_ASSIGN(PipelineController);
+};
+
+}  // namespace media
+
+#endif  // MEDIA_FILTERS_PIPELINE_CONTROLLER_H_