Report VideoDecoder status through ReadCB instead of through FilterHost.

media/base/filters.h

Index: media/base/filters.h
diff --git a/media/base/filters.h b/media/base/filters.h
index b32234f924369adde0fdf9fc7d2618b9f0604002..c53f4eaaa2357b1d1ce02a0e01467f7ff7336c63 100644
--- a/media/base/filters.h
+++ b/media/base/filters.h
@@ -109,6 +109,13 @@ class MEDIA_EXPORT Filter : public base::RefCountedThreadSafe<Filter> {
 
 class MEDIA_EXPORT VideoDecoder : public Filter {

[Ami GONE FROM CHROMIUM, 2012/04/27 16:49:14]

Can you override Filter::set_host() here to LOG(FATAL) to ensure all callers
have been caught?
(with a TODO pointing at the "make a VideoDecoder not a Filter" crbug saying the
override should be removed when this class stops being a Filter).

[xhwang, 2012/04/27 23:22:30]

Done.

  public:
+  // Status codes for read operations on VideoDecoder.
+  enum Status {
+    kOk,  // Everything went as planned.
+    kDecodeError,  // Decoding error happened.
+    kDecryptError  // Decrypting error happened.
+  };
+
   // Initialize a VideoDecoder with the given DemuxerStream, executing the
   // callback upon completion.
   // statistics_cb is used to update global pipeline statistics.
@@ -125,7 +132,7 @@ class MEDIA_EXPORT VideoDecoder : public Filter {
   // Non-NULL frames contain decoded video data or may indicate the  end of
   // the stream. NULL video frames indicate an aborted read. This can happen if
   // the DemuxerStream gets flushed and doesn't have any more data to return.
-  typedef base::Callback<void(scoped_refptr<VideoFrame>)> ReadCB;
+  typedef base::Callback<void(scoped_refptr<VideoFrame>, Status)> ReadCB;

[Ami GONE FROM CHROMIUM, 2012/04/27 16:49:14]

Typically dependent args follow their dependencies, so I'd make Status the first
param, not second.

[scherkus (not reviewing), 2012/04/27 18:27:56]

Building on top of that -- the docs should be updated to mention what to expect
of VideoFrame given the value of Status

[xhwang, 2012/04/27 23:22:30]

Done.

[xhwang, 2012/04/27 23:22:30]

Done.

   virtual void Read(const ReadCB& read_cb) = 0;
 
   // Returns the natural width and height of decoded video in pixels.