Add histogram code for management page

Add a first metric to the chrome://management page which counts how
many times the page is accessed

Bug: 879146
Change-Id: I42be7a314ebffb295069e44735913f49376edda3
Reviewed-on: https://chromium-review.googlesource.com/1243484
Commit-Queue: Stefan Teodorescu <fane@google.com>
Reviewed-by: Steven Bennetts <stevenjb@chromium.org>
Reviewed-by: Steven Holte <holte@chromium.org>
Cr-Commit-Position: refs/heads/master@{#594645}

chrome/browser/ui/webui/management_ui_handler.cc

@@ -9,6 +9,7 @@
 #include "base/bind.h"
 #include "base/bind_helpers.h"
 #include "base/callback.h"
+#include "base/metrics/user_metrics.h"
 #include "base/strings/utf_string_conversions.h"
 #include "base/values.h"
 #include "chrome/browser/browser_process.h"
@@ -113,6 +114,7 @@ void ManagementUIHandler::RegisterMessages() {
 void ManagementUIHandler::HandleGetDeviceManagementStatus(
     const base::ListValue* args) {
   AllowJavascript();
+  base::RecordAction(base::UserMetricsAction("ManagementPageViewed"));
 
 #if defined(OS_CHROMEOS)
   policy::BrowserPolicyConnectorChromeOS* connector =

tools/metrics/actions/actions.xml

@@ -9932,6 +9932,11 @@ should be able to be added at any place in this file.
   </description>
 </action>
 
+<action name="ManagementPageViewed">
+  <owner>hunyadym@chromium.org</owner>
+  <description>The chrome://management page was viewed.</description>
+</action>
+
 <action name="MaxButton_Clk_ExitFS">
   <owner>Please list the metric's owners. Add more owner tags as needed.</owner>
   <description>Please enter the description of this user action.</description>