[GCM] Add port 443 fallback logic and histograms

tools/metrics/histograms/histograms.xml

Index: tools/metrics/histograms/histograms.xml
diff --git a/tools/metrics/histograms/histograms.xml b/tools/metrics/histograms/histograms.xml
index 13febe87bdd144ee592cdb25a190e88e32c5e546..b054620dc332e220bfb28307b4f75b72bb9bcafd 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -6561,11 +6561,24 @@ other types of suffix sets.
   <summary>Status code of the outcome of a GCM checkin request.</summary>
 </histogram>
 
+<histogram name="GCM.ConnectedViaProxy" enum="Boolean">
+  <owner>zea@chromium.org</owner>
+  <summary>Whether the GCM connection was made via a proxy or not.</summary>
+</histogram>
+
 <histogram name="GCM.ConnectionDisconnectErrorCode" enum="NetErrorCodes">
   <owner>zea@chromium.org</owner>
   <summary>Net error results from GCM disconnect events.</summary>
 </histogram>
 
+<histogram name="GCM.ConnectionEndpoint">
+  <owner>zea@chromium.org</owner>
+  <summary>
+    Index of the MCS endpoint to which a connection was made. See
+    gcm_client_impl.cc for endpoint definitions.
+  </summary>
+</histogram>
+
 <histogram name="GCM.ConnectionFailureErrorCode" enum="NetErrorCodes">
   <owner>zea@chromium.org</owner>
   <summary>Net error results from GCM connection attempts.</summary>
@@ -6576,7 +6589,7 @@ other types of suffix sets.
   <summary>Reasons for GCM connection resets.</summary>
 </histogram>
 
-<histogram name="GCM.ConnectionSuccessRate">
+<histogram name="GCM.ConnectionSuccessRate" enum="BooleanSuccess">
   <owner>zea@chromium.org</owner>
   <summary>
     GCM connection success rate. Does not take into account login success. See