media: Support better decoder switching

media/base/video_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_VIDEO_DECODER_H_
 #define MEDIA_BASE_VIDEO_DECODER_H_
 
 #include <string>
 
 #include "base/callback.h"
@@ skipping 26 matching lines @@
   typedef base::Callback<void(DecodeStatus)> DecodeCB;
 
   VideoDecoder();
 
   // 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 ~VideoDecoder();
 
-  // Returns the name of the decoder for logging purpose.
+  // Returns the name of the decoder for logging and decoder selection purposes.
+  // This name should be available immediately after construction (e.g. before
+  // Initialize() is called). It should also be stable in the sense that the
+  // name does not change across multiple constructions.
   virtual std::string GetDisplayName() const = 0;
 
   // Initializes a VideoDecoder with the given |config|, executing the
   // |init_cb| upon completion. |output_cb| is called for each output frame
   // decoded by Decode().
   //
   // If |low_delay| is true then the decoder is not allowed to queue frames,
   // except for out-of-order frames, i.e. if the next frame can be returned it
   // must be returned without waiting for Decode() to be called again.
   // Initialization should fail if |low_delay| is true and the decoder cannot
@@ skipping 55 matching lines @@
   // Returns maximum number of parallel decode requests.
   virtual int GetMaxDecodeRequests() const;
 
  private:
   DISALLOW_COPY_AND_ASSIGN(VideoDecoder);
 };
 
 }  // namespace media
 
 #endif  // MEDIA_BASE_VIDEO_DECODER_H_