Add SIP service into system server.

Change-Id: Icc39e4e54768cfdcc1b20a3efe6206009b9a8d10

core/java/android/content/Context.java

@@ -1545,6 +1545,15 @@ public abstract class Context {
      */
     public static final String DOWNLOAD_SERVICE = "download";
 
+    /**
+     * Use with {@link #getSystemService} to retrieve a
+     * {@link android.net.sip.SipManager} for accessing the SIP related service.
+     *
+     * @see #getSystemService
+     */
+    /** @hide */
+    public static final String SIP_SERVICE = "sip";
+
     /**
      * Determine whether the given permission is allowed for a particular
      * process and user ID running in the system.