Observe screen on/off events in NetworkPolicy.

The POLICY_REJECT_BACKGROUND policy requires that network traffic be
blocked when a UID goes into the background.  Even if the UID has an
activity in the foreground, it's considered "background" if the screen
is turned off.

This changes watches for SCREEN_ON/OFF broadcasts, and rule generation
now observes screen state.  It also introduces an observer pattern so
that ActivityManager doesn't directly know about NetworkPolicy, and
moves the service management into SystemServer.

Change-Id: Ie7a84929d3ca60ae4578d47e19d5a8da10fd8d58
diff --git a/core/java/android/app/IActivityManager.java b/core/java/android/app/IActivityManager.java
index 54c3422..1f53c0e 100644
--- a/core/java/android/app/IActivityManager.java
+++ b/core/java/android/app/IActivityManager.java
@@ -355,6 +355,9 @@
 
     public boolean removeTask(int taskId, int flags) throws RemoteException;
 
+    public void registerProcessObserver(IProcessObserver observer) throws RemoteException;
+    public void unregisterProcessObserver(IProcessObserver observer) throws RemoteException;
+
     /*
      * Private non-Binder interfaces
      */
@@ -577,4 +580,6 @@
     int SWITCH_USER_TRANSACTION = IBinder.FIRST_CALL_TRANSACTION+127;
     int REMOVE_SUB_TASK_TRANSACTION = IBinder.FIRST_CALL_TRANSACTION+128;
     int REMOVE_TASK_TRANSACTION = IBinder.FIRST_CALL_TRANSACTION+129;
+    int REGISTER_PROCESS_OBSERVER_TRANSACTION = IBinder.FIRST_CALL_TRANSACTION+130;
+    int UNREGISTER_PROCESS_OBSERVER_TRANSACTION = IBinder.FIRST_CALL_TRANSACTION+131;
 }