media: Reland "Simplify {Audio|Video}Decoder initialization callback."

media/base/audio_decoder.h

 // Copyright (c) 2012 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_BASE_AUDIO_DECODER_H_
 #define MEDIA_BASE_AUDIO_DECODER_H_
 
 #include <string>
 
 #include "base/callback.h"
 #include "base/memory/ref_counted.h"
 #include "media/base/audio_decoder_config.h"
 #include "media/base/channel_layout.h"
 #include "media/base/decoder_buffer.h"
 #include "media/base/media_export.h"
 #include "media/base/pipeline_status.h"
 
 namespace media {
 
 class AudioBuffer;
 class DemuxerStream;
 
 class MEDIA_EXPORT AudioDecoder {
  public:
   // Status codes for decode operations.
   // TODO(rileya): Now that both AudioDecoder and VideoDecoder Status enums
   // match, break them into a decoder_status.h.
   enum Status {
-    kOk,  // We're all good.
-    kAborted,  // We aborted as a result of Reset() or destruction.
+    kOk,          // We're all good.
+    kAborted,     // We aborted as a result of Reset() or destruction.
     kDecodeError  // A decoding error occurred.
   };
 
+  // Callback for VideoDecoder initialization.
+  typedef base::Callback<void(bool success)> InitCB;
+
   // Callback for AudioDecoder to return a decoded frame whenever it becomes
   // available. Only non-EOS frames should be returned via this callback.
   typedef base::Callback<void(const scoped_refptr<AudioBuffer>&)> OutputCB;
 
   // Callback for Decode(). Called after the decoder has completed decoding
   // corresponding DecoderBuffer, indicating that it's ready to accept another
   // buffer to decode.
   typedef base::Callback<void(Status)> DecodeCB;
 
   AudioDecoder();
 
   // Fires any pending callbacks, stops and destroys the decoder.
   // Note: Since this is a destructor, |this| will be destroyed after this call.
   // Make sure the callbacks fired from this call doesn't post any task that
   // depends on |this|.
   virtual ~AudioDecoder();
 
   // Returns the name of the decoder for logging purpose.
   virtual std::string GetDisplayName() const = 0;
 
   // Initializes an AudioDecoder with the given DemuxerStream, executing the
   // callback upon completion.
-  //  |statistics_cb| is used to update global pipeline statistics.
+  //  |init_cb| is used to return initialization status.
   //  |output_cb| is called for decoded audio buffers (see Decode()).
   virtual void Initialize(const AudioDecoderConfig& config,
-                          const PipelineStatusCB& status_cb,
+                          const InitCB& init_cb,
                           const OutputCB& output_cb) = 0;
 
   // Requests samples to be decoded. Only one decode may be in flight at any
   // given time. Once the buffer is decoded the decoder calls |decode_cb|.
   // |output_cb| specified in Initialize() is called for each decoded buffer,
   // before or after |decode_cb|.
   //
   // Implementations guarantee that the callbacks will not be called from within
   // this method.
   //
   // If |buffer| is an EOS buffer then the decoder must be flushed, i.e.
   // |output_cb| must be called for each frame pending in the queue and
   // |decode_cb| must be called after that.
   virtual void Decode(const scoped_refptr<DecoderBuffer>& buffer,
                       const DecodeCB& decode_cb) = 0;
 
   // Resets decoder state. All pending Decode() requests will be finished or
   // aborted before |closure| is called.
   virtual void Reset(const base::Closure& closure) = 0;
 
  private:
   DISALLOW_COPY_AND_ASSIGN(AudioDecoder);
 };
 
 }  // namespace media
 
 #endif  // MEDIA_BASE_AUDIO_DECODER_H_