Create public EncodedFrame interface.

The plan is to:
 1. Move FrameObject to api/video.
 2. Rename FrameObject to EncodedFrame.
 3. Move EncodedFrame out of the video_coding namespace.

This is the 1st CL.

Bug: webrtc:8909
Change-Id: I2e5100eda6c51bcefb32295e03b73cf1f5c213a4
Reviewed-on: https://webrtc-review.googlesource.com/55560
Commit-Queue: Tommi <tommi@webrtc.org>
Reviewed-by: Tommi <tommi@webrtc.org>
Reviewed-by: Niels Moller <nisse@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#22135}

api/video/encoded_frame.h

@@ -0,0 +1,65 @@
+/*
+ *  Copyright (c) 2016 The WebRTC project authors. All Rights Reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#ifndef API_VIDEO_ENCODED_FRAME_H_
+#define API_VIDEO_ENCODED_FRAME_H_
+
+#include "modules/video_coding/encoded_frame.h"
+
+namespace webrtc {
+namespace video_coding {
+
+// TODO(philipel): Rename FrameObject to EncodedFrame.
+// TODO(philipel): Remove webrtc::VCMEncodedFrame inheritance.
+class FrameObject : public webrtc::VCMEncodedFrame {
+ public:
+  static const uint8_t kMaxFrameReferences = 5;
+
+  FrameObject() = default;
+  virtual ~FrameObject() {}
+
+  virtual bool GetBitstream(uint8_t* destination) const = 0;
+
+  // The capture timestamp of this frame.
+  virtual uint32_t Timestamp() const = 0;
+
+  // When this frame was received.
+  virtual int64_t ReceivedTime() const = 0;
+
+  // When this frame should be rendered.
+  virtual int64_t RenderTime() const = 0;
+
+  // This information is currently needed by the timing calculation class.
+  // TODO(philipel): Remove this function when a new timing class has
+  //                 been implemented.
+  virtual bool delayed_by_retransmission() const { return 0; }
+
+  size_t size() const { return _length; }
+
+  bool is_keyframe() const { return num_references == 0; }
+
+  // The tuple (|picture_id|, |spatial_layer|) uniquely identifies a frame
+  // object. For codec types that don't necessarily have picture ids they
+  // have to be constructed from the header data relevant to that codec.
+  int64_t picture_id = 0;
+  uint8_t spatial_layer = 0;
+  uint32_t timestamp = 0;
+
+  // TODO(philipel): Add simple modify/access functions to prevent adding too
+  // many |references|.
+  size_t num_references = 0;
+  int64_t references[kMaxFrameReferences];
+  bool inter_layer_predicted = false;
+};
+
+}  // namespace video_coding
+}  // namespace webrtc
+
+#endif  // API_VIDEO_ENCODED_FRAME_H_