QUIC enable server push by default. Guarded by FLAGS_quic_enable_server_push_by_default.

net/quic/core/quic_headers_stream.cc

Index: net/quic/core/quic_headers_stream.cc
diff --git a/net/quic/core/quic_headers_stream.cc b/net/quic/core/quic_headers_stream.cc
index 5b011e8cb445713dc667653959029b8760a66d70..a662c4ffea41f790cd88dd9409da825c440eb213 100644
--- a/net/quic/core/quic_headers_stream.cc
+++ b/net/quic/core/quic_headers_stream.cc
@@ -13,6 +13,7 @@
 #include "net/quic/core/quic_bug_tracker.h"
 #include "net/quic/core/quic_flags.h"
 #include "net/quic/core/quic_header_list.h"
+#include "net/quic/core/quic_server_session_base.h"
 #include "net/quic/core/quic_spdy_session.h"
 #include "net/quic/core/quic_time.h"
 #include "net/spdy/spdy_protocol.h"
@@ -196,6 +197,22 @@ class QuicHeadersStream::SpdyFramerVisitor
       case SETTINGS_HEADER_TABLE_SIZE:
         stream_->UpdateHeaderEncoderTableSize(value);
         break;
+      case SETTINGS_ENABLE_PUSH:
+        if (FLAGS_quic_enable_server_push_by_default &&
+            stream_->session()->perspective() == Perspective::IS_SERVER) {
+          // See rfc7540, Section 6.5.2.
+          if (value > 1) {
+            CloseConnection("Invalid value for SETTINGS_ENABLE_PUSH: " +
+                            base::IntToString(value));
+            return;
+          }
+          stream_->UpdateEnableServerPush(value);
+          break;
+        } else {
+          CloseConnection("Unsupported field of HTTP/2 SETTINGS frame: " +
+                          base::IntToString(id));
+        }
+        break;
       // TODO(fayang): Need to support SETTINGS_MAX_HEADER_LIST_SIZE when
       // clients are actually sending it.
       default:
@@ -593,6 +610,10 @@ void QuicHeadersStream::UpdateHeaderEncoderTableSize(uint32_t value) {
   spdy_framer_.UpdateHeaderEncoderTableSize(value);
 }
 
+void QuicHeadersStream::UpdateEnableServerPush(bool value) {
+  spdy_session_->set_server_push_enabled(value);
+}
+
 bool QuicHeadersStream::OnDataFrameHeader(QuicStreamId stream_id,
                                           size_t length,
                                           bool fin) {