Hide multiple-account information if there is only a single account

Adding an API method to telecomm to determine whether there is a single
account.

Bug: 16483795
Change-Id: If30d3a53458b4c784995f3f9e471c8163a8175a4

telecomm/java/android/telecomm/TelecommManager.java

@@ -290,6 +290,16 @@ public class TelecommManager {
         return null;
     }
 
+    /**
+     * Determine whether the device has more than one account registered and enabled.
+     *
+     * @return {@code true} if the device has more than one account registered and enabled and
+     * {@code false} otherwise.
+     */
+    public boolean hasMultipleEnabledAccounts() {
+        return getEnabledPhoneAccounts().size() > 1;
+    }
+
     /**
      * Return the {@link PhoneAccount} for a specified {@link PhoneAccountHandle}. Object includes
      * resources which can be used in a user interface.