[ios clean] Toolbar accessibility and showcase egtests

ios/chrome/app/strings/ios_strings.grd

 <?xml version="1.0" encoding="UTF-8"?>
 
 <!--
 This file contains definition of resources that will be translated for each
 locale.  The strings in this file are specific to iOS.
 -->
 
 <grit base_dir="." latest_public_release="0" current_release="1"
       output_all_resource_defines="false" source_lang_id="en" enc_check="möl">
   <outputs>
@@ skipping 1408 matching lines @@
       </message>
       <message name="IDS_IOS_TOOLBAR_CLOSE_MENU" desc="The accessibility label for the toolbar close settings menu button [iOS only].">
         Close Menu
       </message>
       <message name="IDS_IOS_TOOLBAR_SETTINGS" desc="The accessibility label for the toolbar open settings menu button [iOS only].">
         Menu
       </message>
       <message name="IDS_IOS_TOOLBAR_SHOW_TABS" desc="The accessibility label for the toolbar show tabs button [iOS only].">
         Show Tabs
       </message>
+      <message name="IDS_IOS_TOOLBAR_SHOW_TAB_GRID" desc="The accessibility label for the toolbar show tab grid button [iOS only].">
+        Home

[sczs, 2017/06/20 01:20:30]

Wasn't sure on this one, but I know Tab Grid might not have any meaning for
users. 

[marq (ping after 24h), 2017/06/20 08:13:39]

How is this different from IDS_IOS_TOOLBAR_SHOW_TABS's "show tabs"?

[lpromero, 2017/06/20 08:38:53]

I am not sure of that. The spatial layout is accessible to VoiceOver users when
they drag the finger around the screen. Moreover, Switch Control users can see
but don't interact with the screen.
Adding a concept of "Home" here could well be detrimental for when we introduce
Chrome Home (even though we might not officially name it).

[sczs, 2017/06/21 01:47:56]

I was thinking that Tabs is something most people know about (We don't hace Show
Tab Strip), but the concept of Tab Grid hasn't been introduced yet. 

[sczs, 2017/06/21 01:47:56]

I was actually thinking about that, since that button would take you to Chrome
Home. I wasn't thinking of Switch Control users, thanks for bringing that up.
Will change this to Show Tab Grid, Home doesn't make as much sense as I thought.

+      </message>
       <message name="IDS_IOS_TOOLS_MENU" desc="The accessibility label for the iOS tools menu [iOS only]">
         Tools Menu
       </message>
       <message name="IDS_IOS_TOOLS_MENU_BOOKMARKS" desc="The iOS menu item for opening the bookmarks manager [Length: 15em] [iOS only]">
         Bookmarks
       </message>
       <message name="IDS_IOS_TOOLS_MENU_CLOSE_ALL_INCOGNITO_TABS" desc="The iOS menu item for closing all incognito tabs [Length: 15em] [iOS only]">
         Close All Incognito Tabs
       </message>
       <message name="IDS_IOS_TOOLS_MENU_CLOSE_ALL_TABS" desc="The iOS menu item for closing all tabs [Length: 15em] [iOS only]">
@@ skipping 85 matching lines @@
       </message>
       <message name="IDS_IOS_SYSTEM_MAIL_APP" desc="Name of iOS system-provided Mail app. Note that this is not consistently translated for all locales, e.g. it is still 'Mail' (in English) for French locale, but is translated to '邮件' for Chinese locale. [Length: 10em]">
         Mail
       </message>
       <message name="IDS_IOS_COMPOSE_EMAIL_SETTING" desc="Title for the view and option to select a handler for mailto: URLs. [Length: 20em]">
         Compose Email
       </message>
     </messages>
   </release>
 </grit>