cros: Add enterprise user session metrics

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 47f4d39d47ace9034bb182298b35e380f1b64186..9d8561145dd60905b09929d0305e049982b5c481 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -14147,6 +14147,32 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   </summary>
 </histogram>
 
+<histogram name="Enterprise.PublicSession.SessionLength" units="10-minutes">
+  <owner>xiyuan@chromium.org</owner>
+  <owner>sduraisamy@chromium.org</owner>
+  <summary>
+    A public session starts when a user signs in using the policy configured
+    public account signs in. It stops when the user signs out. Session length is

[Ilya Sherman, 2017/02/15 23:42:44]

nit: "signs in" is repeated twice in this first sentence -- I think one of them
is a typo?

[xiyuan, 2017/02/16 00:21:47]

Apparently I don't read what I typed. :) Done.

+    the time duration between the start and stop events. It is recorded during

[Ilya Sherman, 2017/02/15 23:42:44]

nit: s/time duration/duration

[xiyuan, 2017/02/16 00:21:47]

Done.

+    signing out and reported on the next chrome run. This metric tracks the
+    recorded session length in 10-minute sized bucket and capped at 24 hours.
+  </summary>
+</histogram>
+
+<histogram name="Enterprise.RegularUserSession.SessionLength"
+    units="10-minutes">
+  <owner>xiyuan@chromium.org</owner>
+  <owner>sduraisamy@chromium.org</owner>
+  <summary>
+    A regular user session starts when a user signs in using his/her user
+    account. It stops when the user signs out. Session length is the time
+    duration between the start and stop events. It is recorded during signing
+    out and reported on the next chrome run. This metric tracks the recorded
+    session length on an enrolled device in 10-minute sized bucket and capped at
+    24 hours.

[Ilya Sherman, 2017/02/15 23:42:44]

Do you expect that users often sign out within 24 hours?

[xiyuan, 2017/02/16 00:21:47]

Nope.

The current hypothesis is that public session usually ends within 24 hours but
regular user session would last more than that (IMO, user probably never signs
out, only lock their devices). The UMA is to compare the behavior of the two
types of user sessions and the first 24 hours should be enough to see the
different pattern.

+  </summary>
+</histogram>
+
 <histogram name="Enterprise.SystemLogPIILeak" enum="SystemLogPIIType">
   <obsolete>
     Deprecated and removed from code as of 01/2016.
@@ -14264,6 +14290,13 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   </summary>
 </histogram>
 
+<histogram name="Enterprise.UserSession.Logins"
+    enum="EnterpriseUserSessionLogins">
+  <owner>xiyuan@chromium.org</owner>
+  <owner>sduraisamy@chromium.org</owner>
+  <summary>Tracks the sign-in events on an enrolled device.</summary>
+</histogram>
+
 <histogram name="Enterprise.UserSigninChoice" enum="SigninChoice">
   <owner>atwilson@chromium.org</owner>
   <summary>
@@ -86872,6 +86905,18 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   <int value="11" label="Request interrupted"/>
 </enum>
 
+<enum name="EnterpriseUserSessionLogins" type="int">
+  <summary>
+    Types of sign-in events as defined in
+    chrome/browser/chromeos/login/enterprise_user_session_metrics.h
+  </summary>
+  <int value="0" label="Regular user"/>
+  <int value="1" label="Manual public session"/>
+  <int value="2" label="Automatic public session"/>
+  <int value="3" label="Manual kiosk session"/>
+  <int value="4" label="Automatic kiosk session"/>
+</enum>
+
 <enum name="ErrorCodesGetAdaptersAddresses" type="int">
   <int value="8" label="ERROR_NOT_ENOUGH_MEMORY"/>
   <int value="87" label="ERROR_INVALID_PARAMETER"/>