Add custom action support

chrome/browser/resources/chromeos/chromevox/strings/chromevox_strings.grd

 <?xml version="1.0" encoding="UTF-8"?>
 
 <grit base_dir="." current_release="1" latest_public_release="0"
       output_all_resource_defines="false" enc_check="möl" source_lang_id="en">
   <outputs>
     <output filename="_locales/am/messages.json" type="chrome_messages_json" lang="am"/>
     <output filename="_locales/ar/messages.json" type="chrome_messages_json" lang="ar"/>
     <output filename="_locales/bg/messages.json" type="chrome_messages_json" lang="bg"/>
     <output filename="_locales/bn/messages.json" type="chrome_messages_json" lang="bn"/>
     <output filename="_locales/ca/messages.json" type="chrome_messages_json" lang="ca"/>
@@ skipping 2497 matching lines @@
       </message>
       <message desc="Title displayed in the panel for the speech menu." name="IDS_CHROMEVOX_PANEL_MENU_SPEECH">
         Speech
       </message>
       <message desc="Title displayed in the panel for the tabs menu." name="IDS_CHROMEVOX_PANEL_MENU_TABS">
         Tabs
       </message>
       <message desc="Title displayed in the panel for the ChromeVox menu." name="IDS_CHROMEVOX_PANEL_MENU_CHROMEVOX">
         ChromeVox
       </message>
+      <message desc="Title displayed in the panel for the custom actions menu." name="IDS_CHROMEVOX_PANEL_MENU_CUSTOM_ACTIONS">
+        Custom actions

[dmazzoni, 2017/06/06 03:06:00]

This is fine for this change, but I wonder if it'd be better for users to just
have a single Actions menu and then we could automatically populate it
with whatever actions are available on a given object, including things like
Activate, Focus, etc.

[David Tseng, 2017/06/06 18:12:39]

Perhaps for this change, remove the "custom" part. No need for users to care
that the actions are custom.

[yawano, 2017/06/07 09:30:05]

Okay, let's rename this to "actions". For this CL, only custom actions will be
populated there as we are not sending standard actions at this time. Let's
revisit the UI later how we will show actions in the ChromeVox.

[yawano, 2017/06/08 09:25:28]

Done.

+      </message>
       <message desc="Title displayed in the panel when there are no menu items." name="IDS_CHROMEVOX_PANEL_MENU_ITEM_NONE">
         No items.
       </message>
       <message desc="Title displayed in the panel for the menuitem to report an issue." name="IDS_CHROMEVOX_PANEL_MENU_ITEM_REPORT_ISSUE">
         Report an issue
       </message>
       <message desc="Title of a notification that ChromeVox has been updated." name="IDS_CHROMEVOX_UPDATE_TITLE">
         ChromeVox Updated
       </message>
       <message desc="Message text for a notification that ChromeVox has been updated for a new experience." name="IDS_CHROMEVOX_UPDATE_MESSAGE_NEXT">
@@ skipping 198 matching lines @@
       </message>
       <message desc="Description of a command that toggles text to speech feedback on or off." name="IDS_CHROMEVOX_SPEECH_ON_OFF_DESCRIPTION">
         Toggle speech on or off
       </message>
       <message desc="Description of a command that toggles between 6 and 8 dot braille." name="IDS_CHROMEVOX_TOGGLE_BRAILLE_TABLE">
         Toggle between 6 and 8 dot braille
       </message>
     </messages>
   </release>
 </grit>