Adds a 'Done' button at the end of hats survey

ash/ash_chromeos_strings.grdp

 <?xml version="1.0" encoding="utf-8"?>
 <!-- ChromeOS-specific strings (included from ash_strings.grd).
      Everything in this file is wrapped in <if expr="chromeos">. -->
 <grit-part>
 
   <!-- Device types -->
   <message name="IDS_ASH_CHROMEBASE" desc="The device name for a Chromebase (versus say Chromebox)">
     Chromebase
   </message>
   <message name="IDS_ASH_CHROMEBIT" desc="The device name for a Chromebit (versus say Chromebox)">
@@ skipping 471 matching lines @@
   </message>
 
   <!-- HaTS Strings -->
   <message name="IDS_ASH_HATS_NOTIFICATION_TITLE" desc="The title of the notification for Happiness Tracking Survey.">
     Help us improve Chromebooks
   </message>
   <message name="IDS_ASH_HATS_NOTIFICATION_BODY" desc="The body of the notification for Happiness Tracking Survey.">
     Let us know how we’re doing by answering a few questions.
   </message>
   <message name="IDS_ASH_HATS_NOTIFICATION_TAKE_SURVEY_BUTTON" desc="The title of the button in the notification for Happiness Tracking Survey to take the said survey.">
-    SHOW QUESTIONS
+    Take survey
   </message>
   <message name="IDS_ASH_IME_MENU_ACCESSIBLE_NAME" desc="The accessible text for opt-in IME menu icon in status tray.">
     IME menu button
   </message>
 
   <!-- Quick Unlock Strings -->
    <message name="IDS_ASH_QUICK_UNLOCK_NOTIFICATION_TITLE" desc="The title of the notification for Quick Unlock feature notification.">
     QU Feature notification title here
   </message>
   <message name="IDS_ASH_QUICK_UNLOCK_NOTIFICATION_BODY" desc="The body of the notification for Quick Unlock feature notification.">
@@ skipping 26 matching lines @@
   </message>
   <message name="IDS_DEPRECATED_SHOW_TASK_MANAGER_MSG"
            desc="Notification message to tell users about the deprecation of Shift+ESC shortcut to show the task manager.">
     The shortcut to open the task manager has changed. Please use <ph name="NEW_SHORTCUT">$1<ex>Search+Esc</ex></ph> instead of <ph name="OLD_SHORTCUT">$2<ex>Shift+Esc</ex></ph>.
   </message>
   <message name="IDS_DEPRECATED_NEXT_IME_MSG"
            desc="Notification message to tell users about the deprecation of Shift+Alt shortcut to switch to the next input method.">
     The shortcut to switch to the next input method has changed. Please use <ph name="NEW_SHORTCUT">$1<ex>Ctrl+Shift+Space</ex></ph> instead of <ph name="OLD_SHORTCUT">$2<ex>Shift+Alt</ex></ph>.
   </message>
 </grit-part>