Allow the cast tray to function as expected when the installed extension is missing API methods.

ash/ash_strings.grd

Index: ash/ash_strings.grd
diff --git a/ash/ash_strings.grd b/ash/ash_strings.grd
index b629e110ef74d0a3a4cac783e42609a8fa7fe09b..d997e0c26bfef095d87be8c1d343ac30cee969a8 100644
--- a/ash/ash_strings.grd
+++ b/ash/ash_strings.grd
@@ -278,6 +278,12 @@ Press Ctrl+Alt+Z to disable.
       <message name="IDS_ASH_STATUS_TRAY_CAST_STOP" desc="The label used in the tray popup to stop casting.">
         Stop
       </message>
+      <message name="IDS_ASH_STATUS_TRAY_CAST_UNKNOWN_CAST_TYPE" desc="The label used when we have detected we are casting but do not know if we are casting a tab or the desktop.">
+        Casting
+      </message>
+      <message name="IDS_ASH_STATUS_TRAY_CAST_UNKNOWN_RECEIVER" desc="The label used when we have detected we are casting but do not know the name of the receiver.">
+        Unknown receiver
+      </message>
 
       <message name="IDS_ASH_STATUS_TRAY_BLUETOOTH" desc="The label used as the header in the bluetooth popup.">
         Bluetooth