Enable FLAGS_quic_register_streams_early2, and fix QuicChromiumClientSession

to avoid unregistering static streams with the priority dependency state.

Change-Id: I5dcbfdc3bf08c4b3d18b334c650fe267580f4221
Reviewed-on: https://chromium-review.googlesource.com/1008176Reviewed-by: Zhongyi Shi <zhongyi@chromium.org>
Commit-Queue: Ryan Hamilton <rch@chromium.org>
Cr-Commit-Position: refs/heads/master@{#550095}

net/quic/chromium/quic_chromium_client_session.cc

@@ -930,7 +930,7 @@ void QuicChromiumClientSession::OnHeadersHeadOfLineBlocking(
 
 void QuicChromiumClientSession::UnregisterStreamPriority(QuicStreamId id,
                                                          bool is_static) {
-  if (headers_include_h2_stream_dependency_) {
+  if (headers_include_h2_stream_dependency_ && !is_static) {
     priority_dependency_state_.OnStreamDestruction(id);
   }
   QuicSpdySession::UnregisterStreamPriority(id, is_static);

net/quic/core/quic_flags_list.h

@@ -173,7 +173,7 @@ QUIC_FLAG(
 
 // If true, QUIC streams are registered in the QuicStream constructor instead
 // of in the QuicSpdyStream constructor.
-QUIC_FLAG(bool, FLAGS_quic_reloadable_flag_quic_register_streams_early2, false)
+QUIC_FLAG(bool, FLAGS_quic_reloadable_flag_quic_register_streams_early2, true)
 
 // If this flag and
 // FLAGS_quic_reloadable_flag_quic_fix_write_out_of_order_queued_packet_crash