Add user action for changing the active window in Ash overview mode

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 12159 matching lines @@
 <action name="WindowDrag_MaximizeLeft">
   <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="WindowDrag_MaximizeRight">
   <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="WindowSelector_ActiveWindowChanged">
+  <owner>tdanderson@chromium.org</owner>
+  <owner>bruthig@chromium.org</owner>
+  <description>
+    Recorded when the window that is active prior to entering overview mode is
+    different from the window that is active after exiting overview mode. Note
+    that only normal windows (such as browser and app windows) and panel windows
+    are considered, since these are the only window types shown in overview
+    mode.
+  </description>
+</action>
+
 <action name="WindowSelector_Overview">
   <owner>tdanderson@chromium.org</owner>
   <owner>flackr@chromium.org</owner>
   <description>Starting the window overview mode.</description>
 </action>
 
 <action name="WindowSelector_OverviewEnterKey">
   <owner>tdanderson@chromium.org</owner>
   <owner>flackr@chromium.org</owner>
   <description>
@@ skipping 133 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>