http2: Revert a closed stream cannot receive data

This reverts CL 111676 for golang/go#25023.

Reason for revert: The code change no longer issued a WindowUpdate which
is required when processing data. The original issue found in golang/go#25023
is not present after the revert.

Updates golang/go#28204

Change-Id: Iadbb63d50ca06df1281e699b9ef13181d0593f80
Reviewed-on: https://go-review.googlesource.com/c/153977
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

http2/server.go

@@ -1594,12 +1594,6 @@ func (sc *serverConn) processData(f *DataFrame) error {
 		// type PROTOCOL_ERROR."
 		return ConnectionError(ErrCodeProtocol)
 	}
-	// RFC 7540, sec 6.1: If a DATA frame is received whose stream is not in
-	// "open" or "half-closed (local)" state, the recipient MUST respond with a
-	// stream error (Section 5.4.2) of type STREAM_CLOSED.
-	if state == stateClosed {
-		return streamError(id, ErrCodeStreamClosed)
-	}
 	if st == nil || state != stateOpen || st.gotTrailerHeader || st.resetQueued {
 		// This includes sending a RST_STREAM if the stream is
 		// in stateHalfClosedLocal (which currently means that

http2/server_test.go

@@ -2361,6 +2361,9 @@ func TestServer_NoCrash_HandlerClose_Then_ClientClose(t *testing.T) {
 		// it did before.
 		st.writeData(1, true, []byte("foo"))
 
+		// Get our flow control bytes back, since the handler didn't get them.
+		st.wantWindowUpdate(0, uint32(len("foo")))
+
 		// Sent after a peer sends data anyway (admittedly the
 		// previous RST_STREAM might've still been in-flight),
 		// but they'll get the more friendly 'cancel' code