Android9.0 添加APP后台防杀机制

软件平台：Android9.0

硬件平台：MTK6771

开发过程中遇到在系统资源紧张的时候，后台进程被LMK杀死的情况，下面提供一个防杀策略，供参考：

diff --git a/services/core/java/com/android/server/am/ActivityManagerService.java b/services/core/java/com/android/server/am/ActivityManagerService.java
index 65d75784..bf3bd533 100644
--- a/services/core/java/com/android/server/am/ActivityManagerService.java
+++ b/services/core/java/com/android/server/am/ActivityManagerService.java
@@ -24675,6 +24675,16 @@ public class ActivityManagerService extends IActivityManager.Stub
         int changes = 0;
 
         if (app.curAdj != app.setAdj) {
+            // kbding add this for preventing ocr killing by lmk.
+        &