Fix bug where QUIC_VERSION_21 would stall after sending too many headers.

Merge of internal change 74954339

BUG=412306

Review URL: https://codereview.chromium.org/555143002

Cr-Commit-Position: refs/heads/master@{#293994}

net/quic/quic_session.cc

@@ -272,7 +272,7 @@ void QuicSession::OnWindowUpdateFrames(
       continue;
     }
 
-    if (connection_->version() <= QUIC_VERSION_21 &&
+    if (connection_->version() < QUIC_VERSION_21 &&
         (stream_id == kCryptoStreamId || stream_id == kHeadersStreamId)) {
       DLOG(DFATAL) << "WindowUpdate for stream " << stream_id << " in version "
                    << QuicVersionToString(connection_->version());

net/quic/quic_session_test.cc

@@ -905,6 +905,29 @@ TEST_P(QuicSessionTest, VersionNegotiationDisablesFlowControl) {
   EXPECT_FALSE(stream->flow_controller()->IsEnabled());
 }
 
+TEST_P(QuicSessionTest, WindowUpdateUnblocksHeadersStream) {
+  // Test that a flow control blocked headers stream gets unblocked on recipt of
+  // a WINDOW_UPDATE frame. Regression test for b/17413860.
+  if (version() < QUIC_VERSION_21) {
+    return;
+  }
+
+  // Set the headers stream to be flow control blocked.
+  QuicHeadersStream* headers_stream =
+      QuicSessionPeer::GetHeadersStream(&session_);
+  QuicFlowControllerPeer::SetSendWindowOffset(headers_stream->flow_controller(),
+                                              0);
+  EXPECT_TRUE(headers_stream->flow_controller()->IsBlocked());
+
+  // Unblock the headers stream by supplying a WINDOW_UPDATE.
+  QuicWindowUpdateFrame window_update_frame(headers_stream->id(),
+                                            2 * kDefaultFlowControlSendWindow);
+  vector<QuicWindowUpdateFrame> frames;
+  frames.push_back(window_update_frame);
+  session_.OnWindowUpdateFrames(frames);
+  EXPECT_FALSE(headers_stream->flow_controller()->IsBlocked());
+}
+
 TEST_P(QuicSessionTest, TooManyUnfinishedStreamsCauseConnectionClose) {
   if (version() < QUIC_VERSION_18) {
     return;