QUIC - Don't close the QUIC connection if server config update message

is not handled. Added a histogram to track how often this happens.

R=rch@chromium.org,rjshade@chromium.org,  asvitkine@chromium.org

Review URL: https://codereview.chromium.org/583063002

Cr-Commit-Position: refs/heads/master@{#295824}

net/quic/quic_crypto_client_stream.cc

@@ -448,17 +448,21 @@ void QuicCryptoClientStream::DoHandshakeLoop(
 
 void QuicCryptoClientStream::DoInitializeServerConfigUpdate(
     QuicCryptoClientConfig::CachedState* cached) {
+  bool update_ignored = false;
   if (!server_id_.is_https()) {
     // We don't check the certificates for insecure QUIC connections.
     SetCachedProofValid(cached);
     next_state_ = STATE_VERIFY_PROOF_DONE;
-    return;
-  }
-  if (!cached->IsEmpty() && !cached->signature().empty()) {
+  } else if (!cached->IsEmpty() && !cached->signature().empty()) {
     // Note that we verify the proof even if the cached proof is valid.
     DCHECK(crypto_config_->proof_verifier());
     next_state_ = STATE_VERIFY_PROOF;
+  } else {
+    update_ignored = true;
+    next_state_ = STATE_VERIFY_PROOF_DONE;
   }
+  UMA_HISTOGRAM_BOOLEAN("Net.QuicNumServerConfig.UpdateMessagesIgnored",
+                        update_ignored);
 }
 
 QuicAsyncStatus QuicCryptoClientStream::DoVerifyProof(

tools/metrics/histograms/histograms.xml

@@ -16677,6 +16677,12 @@ Therefore, the affected-histogram name has to have at least one dot in it.
   </summary>
 </histogram>
 
+<histogram name="Net.QuicNumServerConfig.UpdateMessagesIgnored"
+    enum="BooleanIgnored">
+  <owner>rtenneti@chromium.org</owner>
+  <summary>The number of times ServerConfigUpdateMessages ignored.</summary>
+</histogram>
+
 <histogram name="Net.QuicNumStreamFramesInPacket">
   <owner>rch@chromium.org</owner>
   <summary>
@@ -38823,6 +38829,11 @@ Therefore, the affected-histogram name has to have at least one dot in it.
   <int value="1" label="HTTPS"/>
 </enum>
 
+<enum name="BooleanIgnored" type="int">
+  <int value="0" label="Not ignored"/>
+  <int value="1" label="Ignored"/>
+</enum>
+
 <enum name="BooleanLoaded" type="int">
   <int value="0" label="Not loaded"/>
   <int value="1" label="Loaded"/>