Make BaseNetworkObserver available to core code

Currently BaseNetworkObserver is in frameworks/base/services, but
there is code in frameworks/base/core that could use it. This
code typically extends INetworkManagementEventObserver.stub
because BaseNetworkObserver is not available.

Move BaseNetworkObserver to frameworks/base/core without changing
its package name, and use it to simplify two callers. The third
caller, Tethering, is much larger, and I'm not sure it's
appropriate to change it.

Bug: 10232006
Change-Id: Ifc0f2e619e3424e27e35730c048a1cc523df345e

core/java/android/net/EthernetDataTracker.java

@@ -27,6 +27,8 @@ import android.os.RemoteException;
 import android.os.ServiceManager;
 import android.util.Log;
 
+import com.android.server.net.BaseNetworkObserver;
+
 import java.util.concurrent.atomic.AtomicBoolean;
 import java.util.concurrent.atomic.AtomicInteger;
 
@@ -62,7 +64,7 @@ public class EthernetDataTracker implements NetworkStateTracker {
 
     private INetworkManagementService mNMService;
 
-    private static class InterfaceObserver extends INetworkManagementEventObserver.Stub {
+    private static class InterfaceObserver extends BaseNetworkObserver {
         private EthernetDataTracker mTracker;
 
         InterfaceObserver(EthernetDataTracker tracker) {
@@ -70,10 +72,12 @@ public class EthernetDataTracker implements NetworkStateTracker {
             mTracker = tracker;
         }
 
+        @Override
         public void interfaceStatusChanged(String iface, boolean up) {
             Log.d(TAG, "Interface status changed: " + iface + (up ? "up" : "down"));
         }
 
+        @Override
         public void interfaceLinkStateChanged(String iface, boolean up) {
             if (mIface.equals(iface)) {
                 Log.d(TAG, "Interface " + iface + " link " + (up ? "up" : "down"));
@@ -89,21 +93,15 @@ public class EthernetDataTracker implements NetworkStateTracker {
             }
         }
 
+        @Override
         public void interfaceAdded(String iface) {
             mTracker.interfaceAdded(iface);
         }
 
+        @Override
         public void interfaceRemoved(String iface) {
             mTracker.interfaceRemoved(iface);
         }
-
-        public void limitReached(String limitName, String iface) {
-            // Ignored.
-        }
-
-        public void interfaceClassDataActivityChanged(String label, boolean active) {
-            // Ignored.
-        }
     }
 
     private EthernetDataTracker() {