Bug 1381016 - Ensure we process FIN flags on all-padding final frames. r=swu

MozReview-Commit-ID: JuSGsYsmv4n

--HG--
extra : rebase_source : a3c016560cb8209c2e6a55cd05fc6d14d2057402

netwerk/protocol/http/Http2Session.cpp

@@ -3226,7 +3226,10 @@ Http2Session::WriteSegmentsAgain(nsAHttpSegmentWriter *writer,
     LOG3(("Http2Session::WriteSegments %p trying to discard %d bytes of data",
           this, discardCount));
 
-    if (!discardCount) {
+    if (!discardCount && mDownstreamState == DISCARDING_DATA_FRAME) {
+      // Only do this short-cirtuit if we're not discarding a pure padding
+      // frame, as we need to potentially handle the stream FIN in those cases.
+      // See bug 1381016 comment 36 for more details.
       ResetDownstreamState();
       Unused << ResumeRecv();
       return NS_BASE_STREAM_WOULD_BLOCK;