Add UMA metrics for multi-window mode and multi-instance

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 immediately after a user takes the
@@ skipping 837 matching lines @@
   </description>
 </action>
 
 <action name="AlertIndicatorButton_Unmute">
   <owner>miu@chromium.org</owner>
   <description>
     User clicked the tab alert indicator button to unmute the tab.
   </description>
 </action>
 
+<action name="Android.MultiWindowMode.Enter">
+  <owner>twellington@chromium.org</owner>
+  <description>The activity entered Android N multi-window mode.</description>
+</action>
+
+<action name="Android.MultiWindowMode.Enter-SecondInstance">
+  <owner>twellington@chromium.org</owner>
+  <description>
+    The second activity instance (ChromeTabbedActivity2) entered Android N
+    multi-window mode. Recorded separately from Android.MultiWindowMode.Enter to
+    avoid double counting when two instances are running.
+  </description>
+</action>
+
+<action name="Android.MultiWindowMode.Exit">
+  <owner>twellington@chromium.org</owner>
+  <description>The activity exited Android N multi-window mode.</description>
+</action>
+
+<action name="Android.MultiWindowMode.Exit-SecondInstance">
+  <owner>twellington@chromium.org</owner>
+  <description>
+    The second activity instance (ChromeTabbedActivity2) exited Android N
+    multi-window mode. Recorded separately from Android.MultiWindowMode.Exit to
+    avoid double counting when two instances are running.
+  </description>
+</action>
+
+<action name="Android.MultiWindowMode.MultiInstance.Enter">
+  <owner>twellington@chromium.org</owner>
+  <description>
+    A second activity instance (ChromeTabbedActivity2) has been created in
+    Android N multi-window mode.
+  </description>
+</action>
+
 <action name="AppCloseButton_Clk">
   <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="AppList_AutoLaunchCanceled">
   <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 13493 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>