Add metrics for supervised user whitelist installation and uninstallation, and absolute count.

tools/metrics/actions/actions.xml

 <!--
 Copyright 2014 The Chromium Authors. All rights reserved.
 Use of this source code is governed by a BSD-style license that can be
 found in the LICENSE file.
 -->
 
 <!--
 This file is a comprehensive list of Chrome user actions along with the owner
 and description for each user action.
 
@@ skipping 7095 matching lines @@
 <action name="ManagedUsers_UploadItem_Queued">
   <owner>Please list the metric's owners. Add more owner tags as needed.</owner>
   <description>Please enter the description of this user action.</description>
 </action>
 
 <action name="ManagedUsers_UploadItem_Syncing">
   <owner>Please list the metric's owners. Add more owner tags as needed.</owner>
   <description>Please enter the description of this user action.</description>
 </action>
 
+<action name="ManagedUsers_Whitelist_Added">
+  <owner>bauerb@chromium.org</owner>
+  <owner>treib@chromium.org</owner>
+  <owner>pam@chromium.org</owner>
+  <description>
+    A new whitelist has been installed for a supervised user.
+  </description>
+</action>
+
+<action name="ManagedUsers_Whitelist_Removed">
+  <owner>bauerb@chromium.org</owner>
+  <owner>treib@chromium.org</owner>
+  <owner>pam@chromium.org</owner>
+  <description>
+    A new whitelist has been uninstalled for a supervised user.

[Ilya Sherman, 2015/02/06 23:45:47]

nit: I'm not sure what the word "new" means in this sentence -- it might make
more sense without it.

[Bernhard Bauer, 2015/02/08 14:05:33]

You're right, it doesn't make sense; this was copy-and-pasted from above.
Removed.

+  </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>
 </action>
 
 <action name="MaxButton_Clk_Maximize">
   <owner>Please list the metric's owners. Add more owner tags as needed.</owner>
   <description>Please enter the description of this user action.</description>
 </action>
 
@@ skipping 4782 matching lines @@
 <action name="webapps.AddShortcut.Manifest">
   <owner>mlamouri@chromium.org</owner>
   <description>
     Shortcut added to the homescreen with a valid Manifest. This action will be
     recorded in addition to AppShortcut, AppShortcutApple and Bookmark actions
     to keep a trend of whether the webapp also add meta tags.
   </description>
 </action>
 
 </actions>