Creating histograms for roam time for FT and non-FT networks

Creating histograms for roam time for FT and non-FT networks and for
PSK and 802.1X authentication. This is a success metric to quantify
roaming time improvements from FT. Histograms are implemented in
CL:957442

Bug: 791202
Change-Id: I0afed4ef74080d32b24088cc34636ead1367e5b4
Reviewed-on: https://chromium-review.googlesource.com/957703
Commit-Queue: Matthew Wang <matthewmwang@chromium.org>
Reviewed-by: Ilya Sherman <isherman@chromium.org>
Cr-Commit-Position: refs/heads/master@{#549401}

tools/metrics/histograms/histograms.xml

@@ -53250,6 +53250,17 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   </summary>
 </histogram>
 
+<histogram base="true" name="Network.Shill.WiFi.RoamTime" units="ms">
+<!-- Name completed by histogram_suffixes name="RoamSecurityType" -->
+
+  <owner>matthewmwang@chromium.org</owner>
+  <summary>
+    Chrome OS network metric recording roam time in milliseconds. This is
+    recorded every time a successful roam from one wireless access point to
+    another occurs.
+  </summary>
+</histogram>
+
 <histogram name="Network.Shill.WiFi.ScanResult" enum="WiFiScanResult">
   <owner>kirtika@chromium.org</owner>
   <summary>
@@ -115196,6 +115207,22 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   <affected-histogram name="PreloadScanner.Counts2.Miss"/>
 </histogram_suffixes>
 
+<histogram_suffixes name="RoamSecurityType" separator=".">
+  <suffix name="EAP"
+      label="Records roams in a network using 802.1X authentication without
+             Fast Transition"/>
+  <suffix name="FTEAP"
+      label="Records roams in a network using 802.1X authentication with Fast
+             Transition"/>
+  <suffix name="FTPSK"
+      label="Records roams in a network using PSK authentication with Fast
+             Transition"/>
+  <suffix name="PSK"
+      label="Records roams in a network using PSK authentication without Fast
+             Transition"/>
+  <affected-histogram name="Network.Shill.WiFi.RoamTime"/>
+</histogram_suffixes>
+
 <histogram_suffixes name="SafeBrowsing.V4Store.Metrics" separator=".">
   <suffix name="AnyIpMalware" label="(Obsolete. Was: AnyIpMalware)"/>
   <suffix name="CertCsdDownloadWhitelist"/>