Various tweaks to try to improve low memory behavior.

- Reduce the amount that we ask processes to GC after a significant
  operation occurs, but introducing a minimum time between GCs and
  using this in various ways to schedule them.

- Don't spam all of the processes with onLowMemory().  Now deliver
  these using the same gc facility, so we do the processes one at a
  time, and don't allow the same process to get this call more than
  once a minute.

- Increase the time a service must run before we will reset its
  restart delay to 30 minutes (from 10).

- Increase the restart delay multiplication factor from 2 to 4.

- Ensure that we don't restart more than one service every 10 seconds
  (unless some external event causes a service's process to be started
  for some other reason of course).

- Increase the amount of time that a service must run before we
  decide to lower it to a background process.

And some other things:

- Catch IllegalArgumentException in ViewRoot like we do for no
  resources to avoid the system process crashing.

- Fix a number of places where we were missing breaks between the
  activity manager's message dispatch func(!!).

- Fix reason printed for processes in the background.

- Print the list of processing waiting to GC.

services/java/com/android/server/SystemServer.java

@@ -19,7 +19,6 @@ package com.android.server;
 import com.android.server.am.ActivityManagerService;
 import com.android.server.status.StatusBarService;
 
-import dalvik.system.PathClassLoader;
 import dalvik.system.VMRuntime;
 
 import android.app.ActivityManagerNative;
@@ -32,7 +31,6 @@ import android.content.pm.IPackageManager;
 import android.database.ContentObserver;
 import android.database.Cursor;
 import android.media.AudioService;
-import android.os.IBinder;
 import android.os.Looper;
 import android.os.RemoteException;
 import android.os.ServiceManager;
@@ -46,9 +44,6 @@ import android.server.search.SearchManagerService;
 import android.util.EventLog;
 import android.util.Log;
 
-import java.lang.reflect.Constructor;
-import java.lang.reflect.InvocationTargetException;
-
 class ServerThread extends Thread {
     private static final String TAG = "SystemServer";
     private final static boolean INCLUDE_DEMO = false;