Deprecate histogram: Net.QuicSession.SentConnectivityProbe as INTERNAL_ERROR spike was understood.

Bug: 817496
Change-Id: Ic382ff347fdec75093019954c75c25fbe17ee0e2
Reviewed-on: https://chromium-review.googlesource.com/972423Reviewed-by: Ryan Hamilton <rch@chromium.org>
Reviewed-by: Alexei Svitkine <asvitkine@chromium.org>
Commit-Queue: Zhongyi Shi <zhongyi@chromium.org>
Cr-Commit-Position: refs/heads/master@{#544898}

net/quic/core/quic_connection.cc

@@ -2673,9 +2673,6 @@ bool QuicConnection::SendConnectivityProbingPacket(
     QuicPacketWriter* probing_writer,
     const QuicSocketAddress& peer_address) {
   DCHECK(peer_address.IsInitialized());
-  // TODO(zhongyi): remove this histogram once the cause of the INTERNAL_ERROR
-  // increase is determined.
-  UMA_HISTOGRAM_BOOLEAN("Net.QuicSession.SentConnectivityProbe", true);
   if (always_discard_packets_after_close_ && !connected_) {
     QUIC_FLAG_COUNT_N(
         quic_reloadable_flag_quic_always_discard_packets_after_close, 2, 2);

tools/metrics/histograms/histograms.xml

@@ -48064,6 +48064,9 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
 </histogram>
 
 <histogram name="Net.QuicSession.SentConnectivityProbe" enum="Boolean">
+  <obsolete>
+    Deprecated 03/2018 as crbug.com/817496 is resolved.
+  </obsolete>
   <owner>zhongyi@chromium.org</owner>
   <summary>
     The number of times the connection sends connectivity probe to the peer.