arc: Improve copy on error cases in opt-in flow

chrome/app/chromeos_strings.grdp

 <?xml version="1.0" encoding="utf-8"?>
 <!-- ChromeOS-specific strings (included from generated_resources.grd).
      Everything in this file is wrapped in <if expr="chromeos">. -->
 <grit-part>
   <message name="IDS_EMPTY_STRING" desc="Empty string, exist only to make code generic. No translation required.">
   </message>
   <!-- Idle logout dialog for retail mode -->
   <message name="IDS_IDLE_LOGOUT_TITLE" desc="Dialog title for the idle logout dialog. Used in retail mode only.">
     Are you still there?
   </message>
@@ skipping 6651 matching lines @@
   <message name="IDS_ARC_OPT_IN_DIALOG_DESCRIPTION" desc="Description of the opt-in dialog for Android apps.">
     Choose from over a million apps and games on Google Play to install and use on your <ph name="DEVICE_TYPE">$1<ex>Chromebook</ex></ph>.
   </message>
   <message name="IDS_ARC_OPT_IN_DIALOG_BUTTON_AGREE" desc="Agree button of the opt-in dialog for Android apps.">
     Agree
   </message>
   <message name="IDS_ARC_OPT_IN_DIALOG_BUTTON_CANCEL" desc="Cancel button of the opt-in dialog for Android apps.">
     Cancel
   </message>
   <message name="IDS_ARC_OPT_IN_DIALOG_BUTTON_RETRY" desc="Retry button of the opt-in dialog for Android apps.">
-    Retry
+    Try again
   </message>
   <message name="IDS_ARC_OPT_IN_DIALOG_BUTTON_SEND_FEEDBACK" desc="Send feedback button of the opt-in dialog for Android apps.">
     Send feedback
   </message>
   <message name="IDS_ARC_OPT_IN_DIALOG_PROGRESS_LSO" desc="Name of LSO loading progress of the opt-in dialog for Android apps.">
     Just a sec...
   </message>
   <message name="IDS_ARC_OPT_IN_DIALOG_PROGRESS_ANDROID" desc="Name of Android loading progress of the opt-in dialog for Android apps.">
     This may take up to a minute or so...
   </message>
@@ skipping 31 matching lines @@
   <message name="IDS_ARC_OPT_OUT_DIALOG_BUTTON_CONFIRM_DISABLE" desc="Button to confirm that play store should be removed from this device">
     Remove Android apps
   </message>
   <message name="IDS_ARC_OPT_OUT_DIALOG_BUTTON_CANCEL" desc="Button to cancel the removal of the play store from this device">
     Cancel
   </message>
   <message name="IDS_ARC_SIGN_IN_NETWORK_ERROR" desc="Android sign-in error because of network error">
     Network error
   </message>
   <message name="IDS_ARC_SIGN_IN_SERVICE_UNAVAILABLE_ERROR" desc="Android sign-in error because of service is unavailable">
-    Service unavailable
+    Couldn't reach Google Play. Try again now.
   </message>
   <message name="IDS_ARC_SIGN_IN_BAD_AUTHENTICATION_ERROR" desc="Android sign-in error because of bad authentification">
     Bad authentication
   </message>
   <message name="IDS_ARC_SIGN_IN_GMS_NOT_AVAILABLE_ERROR" desc="Android sign-in error because of GMS services are unavailable">
     GMS services are unavailable
   </message>
   <message name="IDS_ARC_SIGN_IN_CLOUD_PROVISION_FLOW_FAIL_ERROR" desc="Android sign-in error because of cloud provision flow failed">
     Cloud provision flow failed
   </message>
@@ skipping 21 matching lines @@
   <message name="IDS_CRITICALLY_LOW_DISK_NOTIFICATION_TITLE" desc="Title of the notification warning users that they are critically low on disk space.">
     Device disk space critically low
   </message>
   <message name="IDS_CRITICALLY_LOW_DISK_NOTIFICATION_MESSAGE" desc="Notification text warning users that they are critically low on disk space.">
     Free up disk space or device will become unresponsive.
   </message>
   <message name="IDS_LOW_DISK_NOTIFICATION_BUTTON" desc="Button on the low disk notification to open storage management.">
     Manage storage
   </message>
 </grit-part>