Add use counters for persistent notification interaction.

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. A user action should be tied to an actual
 action taken by a user. It should be logged immediatly after a user takes the
@@ skipping 8564 matching lines @@
   <description>Please enter the description of this user action.</description>
 </action>
 
 <action name="Notifications.Mute">
   <owner>dewittj@chromium.org</owner>
   <description>
     Recorded when a user enables the message center's Do Not Disturb mode.
   </description>
 </action>
 
+<action name="Notifications.Persistent.Clicked">
+  <owner>peter@chromium.org</owner>
+  <description>
+    Recorded when a persistent notification gets clicked on by the user.
+  </description>
+</action>
+
+<action name="Notifications.Persistent.Closed">
+  <owner>peter@chromium.org</owner>
+  <description>
+    Recorded when a persistent notification gets closed by the user. Note that
+    this is not mutually exclusive with clicked notifications if the website
+    does not close the notification on click.

[Ilya Sherman, 2015/09/01 23:02:53]

This sentence confuses me.  If a website does close the notification on click,
do both actions get recorded, or just one of them?

[Peter Beverloo, 2015/09/02 12:48:06]

This is about user-initiated responses, so then only one would be recorded. I
have clarified the message.

+  </description>
+</action>
+
+<action name="Notifications.Persistent.Shown">
+  <owner>peter@chromium.org</owner>
+  <description>Recorded when a persistent notification gets shown.</description>
+</action>
+
 <action name="Notifications.ShowMessageCenter">
   <owner>dewittj@chromium.org</owner>
   <description>
     Recorded when the message center screen is being presented to the user.
   </description>
 </action>
 
 <action name="Notifications.ShowSettings">
   <owner>dewittj@chromium.org</owner>
   <description>
@@ skipping 4134 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>