Add DNS_TETHER to the list of UIDs in the framework.

It has been reserved in android_filesystem_config.h since
aosp/245632 in 2016, but was never included in the list of UIDs
in Process.java.

Bug: 29881876
Test: builds, boots
Change-Id: I6d36d7d15634445d992a10087b5ba31b480f9f20

core/java/android/os/Process.java

@@ -139,6 +139,12 @@ public class Process {
      */
     public static final int CAMERASERVER_UID = 1047;
 
+    /**
+     * Defines the UID/GID for the tethering DNS resolver (currently dnsmasq).
+     * @hide
+     */
+    public static final int DNS_TETHER_UID = 1052;
+
     /**
      * Defines the UID/GID for the WebView zygote process.
      * @hide