Allow add to homescreen and app banner strings to be changed via variations.

chrome/android/java/strings/android_chrome_strings.grd

 <?xml version="1.0" encoding="UTF-8"?>
 
 <!-- android_chrome_strings.grd contains strings for Chrome for Android.
 
 FAQ:
   - How do I add, change, or remove a string?
       Just update this file.
   - Translations will happen automatically??
       Yes, indeed. Just add your string before the branch point and
       make the description good.
@@ skipping 1540 matching lines @@
 
       <!-- Android NFC Beam strings -->
       <message name="IDS_NFC_BEAM_ERROR_OVERLAY_ACTIVE" desc="Android Beam error - a tab is not in the foreground [CHAR-LIMIT=40]">
         Select a tab to beam
       </message>
       <message name="IDS_NFC_BEAM_ERROR_BAD_URL" desc="Android Beam error - the current tab has an invalid url [CHAR-LIMIT=40]">
         Can’t beam current tab
       </message>
 
       <!-- Add to Home screen strings -->
-      <message name="IDS_MENU_ADD_TO_HOMESCREEN" desc="Menu item for adding a shortcut to the Home screen. [CHAR-LIMIT=27]">
+      <message name="IDS_MENU_ADD_TO_HOMESCREEN" desc="Menu item for adding a shortcut to the Home screen (default title). [CHAR-LIMIT=27]">
         Add to Home screen
       </message>
+      <message name="IDS_MENU_ADD_TO_HOMESCREEN_ADD" desc="Menu item for adding a shortcut to the Home screen. [CHAR-LIMIT=27]">
+        Add shortcut
+      </message>
+      <message name="IDS_MENU_ADD_TO_HOMESCREEN_INSTALL" desc="Menu item for adding a shortcut to the Home screen. [CHAR-LIMIT=27]">
+        Install web app
+      </message>
+      <message name="IDS_APP_BANNER_ADD" desc="A button in an app banner to confirm adding a site to homescreen">
+        Add
+      </message>
+      <message name="IDS_APP_BANNER_INSTALL" desc="A button in an app banner to confirm adding a site to homescreen">
+        Install
+      </message>
       <message name="IDS_ADDED_TO_HOMESCREEN" desc="Indicates that the website with the specified name was added to the user's Home screen.">
         <ph name="NAME">%1$s<ex>Google</ex></ph> was added to your Home screen
       </message>
       <message name="IDS_FAIL_TO_INSTALL_WEBAPK" desc="The installation of a WebAPK fails. [CHAR-LIMIT=27]">
         Unable to add
       </message>
 
       <!-- WebsiteSettingsPopup (PageInfo dialog) -->
       <message name="IDS_PAGE_INFO_SITE_SETTINGS_BUTTON" desc="Text in the button that opens a website's Site Settings from the Page Info dialog.">
         Site Settings
@@ skipping 1128 matching lines @@
       <message name="IDS_ITEM_CHOOSER_ITEM_NAME_WITH_ID" desc="To distinguish items with the same name, the item chooser shows the item name with id.">
         <ph name="ITEM_NAME">%1$s<ex>item_name</ex></ph> (<ph name="ITEM_ID">%2$s<ex>item id</ex></ph>)
       </message>
 
       <message name="IDS_INSTANT_APPS_OPEN_IN_APP" desc="Button label for the user action that will open an Instant App.">
         Open app
       </message>
     </messages>
   </release>
 </grit>