Add a new SpdyStream::Delegate method to handle trailers

net/spdy/spdy_stream.h

Index: net/spdy/spdy_stream.h
diff --git a/net/spdy/spdy_stream.h b/net/spdy/spdy_stream.h
index 4c01e0cecef2c2234fdf9eea32b4a8a4fe4a1c93..190e2b4b09d8f5153b0f07c25d1e973ec5dd1e7b 100644
--- a/net/spdy/spdy_stream.h
+++ b/net/spdy/spdy_stream.h
@@ -57,7 +57,8 @@ enum SpdySendStatus {
 // whether the current response headers are complete or not.

[Ryan Hamilton, 2015/08/10 17:23:25]

Please update this comment to reflect the meaning of the new TRAILERS_RECEIVED
state. Also, it would be great to explain here (or elsewhere) when it's possible
to received HEADERS. It looks like only before any DATA or after all DATA. Is
that right?

[xunjieli, 2015/08/10 20:31:07]

Done. Good catch! I also updated comments below.

 enum SpdyResponseHeadersStatus {
   RESPONSE_HEADERS_ARE_INCOMPLETE,
-  RESPONSE_HEADERS_ARE_COMPLETE
+  RESPONSE_HEADERS_ARE_COMPLETE,
+  TRAILERS_RECEIVED,
 };
 
 // The SpdyStream is used by the SpdySession to represent each stream known
@@ -139,6 +140,10 @@ class NET_EXPORT_PRIVATE SpdyStream {
     // closed.
     virtual void OnDataSent() = 0;
 
+    // Called when trailers are received. Note that trailers HEADER frame will
+    // have END_STREAM flag set, so this will be followed by OnClose.
+    virtual void OnTrailers(const SpdyHeaderBlock& trailers);

[Ryan Hamilton, 2015/08/10 17:23:25]

Is it required by the spec that trailers have the END_STREAM flag set, or is
this convention? Looks like section 8.1 of the HTTP/2 RFC requires END_STREAM be
set?

[Ryan Hamilton, 2015/08/10 17:23:25]

I think this should be = 0 (pure virtual), shouldn't it?

[xunjieli, 2015/08/10 20:31:07]

Done. I was not sure if all implementations should care about trailers.

[xunjieli, 2015/08/10 20:31:07]

The RFC says "The HEADERS frame starting the trailers header block has the
END_STREAM flag set." I think it is required that trailers header block has
END_STREAM flag. I edited the comment to make it clearer.

+
     // Called when SpdyStream is closed. No other delegate functions
     // will be called after this is called, and the delegate must not
     // access the stream after this is called. Must not cause the