Avoids the "re-encode HPACK as SPDY3" step.

net/quic/quic_chromium_client_stream.cc

Index: net/quic/quic_chromium_client_stream.cc
diff --git a/net/quic/quic_chromium_client_stream.cc b/net/quic/quic_chromium_client_stream.cc
index 1aa8e531fcfe01f530896168256a801ba5d84c30..cd883149a3263f4e2602e407f7983ba309764294 100644
--- a/net/quic/quic_chromium_client_stream.cc
+++ b/net/quic/quic_chromium_client_stream.cc
@@ -14,6 +14,7 @@
 #include "net/quic/quic_spdy_session.h"
 #include "net/quic/quic_write_blocked_list.h"
 #include "net/quic/spdy_utils.h"
+#include "net/spdy/header_coalescer.h"
 
 namespace net {
 
@@ -60,6 +61,28 @@ void QuicChromiumClientStream::OnStreamHeadersComplete(bool fin,
   }
 }
 
+void QuicChromiumClientStream::OnStreamHeaderList(
+    bool fin,
+    size_t frame_len,
+    const QuicHeaderList& header_list) {
+  QuicSpdyStream::OnStreamHeaderList(fin, frame_len, header_list);
+
+  if (headers_delivered_) {
+    // The delegate will read the trailers via a posted task.
+    NotifyDelegateOfHeadersCompleteLater(received_trailers(), frame_len);
+  } else {
+    HeaderCoalescer coalescer;
+    for (const auto& header : header_list) {
+      coalescer.OnHeader(header.first, header.second);
+    }
+    ConsumeHeaderList();
+    session_->OnInitialHeadersComplete(id(), coalescer.headers());
+
+    // The delegate will read the headers via a posted task.
+    NotifyDelegateOfHeadersCompleteLater(coalescer.headers(), frame_len);
+  }
+}
+
 void QuicChromiumClientStream::OnPromiseHeadersComplete(
     QuicStreamId promised_id,
     size_t frame_len) {
@@ -222,6 +245,7 @@ void QuicChromiumClientStream::NotifyDelegateOfHeadersComplete(
   // Only mark trailers consumed when we are about to notify delegate.
   if (headers_delivered_) {
     MarkTrailersConsumed(decompressed_trailers().length());
+    MarkTrailersDelivered();
     net_log_.AddEvent(
         NetLog::TYPE_QUIC_CHROMIUM_CLIENT_STREAM_READ_RESPONSE_TRAILERS,
         base::Bind(&SpdyHeaderBlockNetLogCallback, &headers));