Allow default SMS app to get self phone number

Apps with WRITE_SMS app op can now call TelephonyManager.getLine1Number().
(Note we no longer have the WRITE_SMS permission.)

Bug 22031904

Change-Id: Ic843b6d7674879951a64e3b3a92bca09c3b5c65b

telephony/java/android/telephony/TelephonyManager.java

@@ -2011,6 +2011,8 @@ public class TelephonyManager {
      * <p>
      * Requires Permission:
      *   {@link android.Manifest.permission#READ_PHONE_STATE READ_PHONE_STATE}
+     * <p>
+     * The default SMS app can also use this.
      */
     public String getLine1Number() {
         return getLine1NumberForSubscriber(getDefaultSubscription());
@@ -2022,6 +2024,8 @@ public class TelephonyManager {
      * <p>
      * Requires Permission:
      *   {@link android.Manifest.permission#READ_PHONE_STATE READ_PHONE_STATE}
+     * <p>
+     * The default SMS app can also use this.
      *
      * @param subId whose phone number for line 1 is returned
      */