Add WiFi remembered network count metric

BUG=396785
R=isherman@chromium.org

Review URL: https://codereview.chromium.org/417813002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@285714 0039d316-1c4b-4281-b951-d872f2087c98

tools/metrics/histograms/histograms.xml

@@ -17899,6 +17899,16 @@ Therefore, the affected-histogram name has to have at least one dot in it.
   </summary>
 </histogram>
 
+<histogram name="Network.Shill.WiFi.RememberedNetworkCount">
+  <owner>pstew@chromium.org</owner>
+  <summary>
+    Chrome OS network diagnostic metric sampling the number of 802.11 wireless
+    networks known by the connection manager at the time a configuration profile
+    has been loaded.  A configuration profile is loaded at each system startup,
+    and when a user logs in.
+  </summary>
+</histogram>
+
 <histogram name="Network.Shill.WiFi.ScanResult" enum="WiFiScanResult">
   <owner>quiche@chromium.org</owner>
   <summary>