Take screenshot of active window

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 687 matching lines @@
 <action name="Accel_Take_Partial_Screenshot">
   <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="Accel_Take_Screenshot">
   <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="Accel_Take_Window_Screenshot">
+  <owner>warx@chromium.org</owner>
+  <description>
+    Metric recorded when shortcut key to initiate an active window screenshot.
+  </description>
+</action>
+
 <action name="Accel_Toggle_Caps_Lock">
   <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="Accel_Toggle_Maximized">
   <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 11339 matching lines @@
 <action name="Screenshot_TakeFull">
   <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="Screenshot_TakePartial">
   <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="Screenshot_TakeWindow">
+  <owner>warx@chromium.org</owner>
+  <description>User initiates an active window screenshot.</description>

[oshima, 2016/04/13 23:05:37]

"a window screenshot"

I'll add a window selection per kuscher@'s request.

[Qiang(Joe) Xu, 2016/04/13 23:36:16]

Done.

+</action>
+
 <action name="SearchWithRLZ">
   <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="SearchWithoutRLZ">
   <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 1967 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>