Add Ctrl+Alt+H as global shortcut to toggle high contrast 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. 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 871 matching lines @@
     Metric recorded when shortcut key to initiate an active window screenshot
     per kuscher@'s request.
   </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_High_Contrast">
+  <owner>dmazzoni@chromium.org</owner>
+  <description>
+    Metric recorded when the user toggles Chrome OS High Contrast mode with the
+    keyboard accelerator (Ctrl+Alt+H).
+  </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>
 
 <action name="Accel_Toggle_Minimized">
   <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_Minimized_M">
   <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_Minimized_Minus">
   <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_Mirror_Mode">
   <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_Spoken_Feedback">
-  <owner>Please list the metric's owners. Add more owner tags as needed.</owner>
-  <description>Please enter the description of this user action.</description>
+  <owner>dmazzoni@chromium.org</owner>
+  <description>Toggles Spoken Feedback (ChromeVox)</description>
 </action>
 
 <action name="Accel_Toggle_Touchpad">
   <owner>afakhry@chromium.org</owner>
   <description>
     Metric recorded when the user toggles the touchpad status using the
     debugging accelerator.
   </description>
 </action>
 
@@ skipping 14800 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>