Add GetUrl to DemuxerStreamProvider interface

media/base/demuxer_stream_provider.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 MEDIA_BASE_DEMUXER_STREAM_PROVIDER_H_
 #define MEDIA_BASE_DEMUXER_STREAM_PROVIDER_H_
 
 #include "base/macros.h"
 #include "media/base/demuxer_stream.h"
 #include "media/base/media_export.h"
+#include "url/gurl.h"
 
 namespace media {
 
+// Abstract class that defines how to retrieve "media sources" in DemuxerStream
+// form (for most cases) or URL form (for the MediaPlayerRenderer case).
+//
+// The sub-classes do not stricly provide demuxer streams, but because all
+// sub-classes are for the moment Demuxers, this class has not been renamed to
+// "MediaProvider". This class would be a good candidate for renaming, if
+// ever Pipeline were to support this class directly, instead of the Demuxer
+// interface.
+//
+// The derived classes must return a non-null value for the getter method
+// associated with their type, and return a null/empty value for other getters.
 class MEDIA_EXPORT DemuxerStreamProvider {
  public:
+  enum Type {
+    STREAM,  // Indicates GetStream() should be used
+    URL,     // Indicates GetUrl() should be used
+  };
+
   DemuxerStreamProvider();
   virtual ~DemuxerStreamProvider();
 
-  // Returns the first stream of the given stream type (which is not allowed
-  // to be DemuxerStream::TEXT), or NULL if that type of stream is not present.
+  // For Type::STREAM:
+  //   Returns the first stream of the given stream type (which is not allowed
+  //   to be DemuxerStream::TEXT), or NULL if that type of stream is not
+  //   present.
+  // Other types:
+  //   Should not be called.
   virtual DemuxerStream* GetStream(DemuxerStream::Type type) = 0;
 
+  // For Type::URL:
+  //   Returns the URL of the media to play. This might be an empty URL, and
+  //   should be handled appropriately by the caller.
+  // Other types:
+  //   Should not be called.
+  virtual GURL GetUrl() const;
+
+  virtual DemuxerStreamProvider::Type GetType() const;
+
  private:
   DISALLOW_COPY_AND_ASSIGN(DemuxerStreamProvider);
 };
 
 }  // namespace media
 
 #endif  // MEDIA_BASE_DEMUXER_STREAM_PROVIDER_H_