Add GetUrl to DemuxerStreamProvider interface

media/base/demuxer_stream_provider.h

Index: media/base/demuxer_stream_provider.h
diff --git a/media/base/demuxer_stream_provider.h b/media/base/demuxer_stream_provider.h
index e5289f3da45f8201879a873faa54b88e288c8277..c2c191f83c14013d279ea37ac0fc5bd654b8b2fa 100644
--- a/media/base/demuxer_stream_provider.h
+++ b/media/base/demuxer_stream_provider.h
@@ -8,18 +8,47 @@
 #include "base/macros.h"
 #include "media/base/demuxer_stream.h"
 #include "media/base/media_export.h"
+#include "url/gurl.h"
 
 namespace media {
 
+// Interface 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 interface would be a good candidate for renaming, if
+// ever Pipeline were to use this interface directly, instead of the Demuxer
+// interface.
+//
+// The derived classes must return a non-null value for either of the getter
+// methods, and return a null value for the other.
+// Ex: A Demuxer should return the DemuxerStreams it supports, but return a
+// empty URL.
 class MEDIA_EXPORT DemuxerStreamProvider {
  public:
+  enum Type {
+    STREAM,  // Indicates GetStream() should be used
+    URL,     // Indicated 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.
+  // Returns a null value if we are of Type::URL.

[xhwang, 2016/06/24 03:19:47]

You can say that if type is not STREAM, this should not be called. Then we can
just DCHECK/NOTREACHED in impl.

[tguilbert, 2016/06/24 21:18:42]

Done.

   virtual DemuxerStream* GetStream(DemuxerStream::Type type) = 0;
 
+  // Returns the URL of the media to play. To be used when DemuxerStreams are
+  // not relevant (e.g. in the MediaPlayerRender case).
+  // Returns an empty GURL if we are of Type::STREAM.

[xhwang, 2016/06/24 03:19:47]

ditto

[tguilbert, 2016/06/24 21:18:43]

Done.

+  virtual GURL GetUrl() { return GURL(); };

[xhwang, 2016/06/24 03:19:47]

remote the trailing semicolon, ditto on l.50

[DaleCurtis, 2016/06/24 17:43:41]

Virtual methods should never be inline per the style guide.

[tguilbert, 2016/06/24 21:18:43]

Done.

[tguilbert, 2016/06/24 21:18:43]

Done.

+
+  // Returns the type of the DemuxerStreamProvider.
+  // The type also indicates whether GetStream or GetUrl should be used.
+  virtual DemuxerStreamProvider::Type type() { return Type::STREAM; };

[xhwang, 2016/06/24 03:19:47]

nit: 

Will this work?

Type type() { return STREAM; }

[tguilbert, 2016/06/24 21:18:43]

It does.

+
  private:
   DISALLOW_COPY_AND_ASSIGN(DemuxerStreamProvider);
 };