Keep DisplayAreaGroup and DisplayAreaPolicyBuilder in services.jar

After aosp/2123992, this 2 classes are not visible by
CarDisplayAreaPolicyProvider, result in boot loop.

Use @Keep to keep them in services.jar solve the booting issue.

Fix: 239744560
Test: Manually luanch seahawk_car_ui_portrait
Change-Id: Ie4c934b7c729017e2bd0ff8cf99d059cf9275da3
diff --git a/services/core/java/com/android/server/wm/DisplayAreaGroup.java b/services/core/java/com/android/server/wm/DisplayAreaGroup.java
index 8488314..705327d 100644
--- a/services/core/java/com/android/server/wm/DisplayAreaGroup.java
+++ b/services/core/java/com/android/server/wm/DisplayAreaGroup.java
@@ -25,7 +25,10 @@
 import android.content.res.Configuration;
 import android.graphics.Rect;
 
+import com.android.internal.annotations.Keep;
+
 /** The root of a partition of the logical display. */
+@Keep
 class DisplayAreaGroup extends RootDisplayArea {
 
     DisplayAreaGroup(WindowManagerService wms, String name, int featureId) {
diff --git a/services/core/java/com/android/server/wm/DisplayAreaPolicyBuilder.java b/services/core/java/com/android/server/wm/DisplayAreaPolicyBuilder.java
index 8e21d96..f49e64e 100644
--- a/services/core/java/com/android/server/wm/DisplayAreaPolicyBuilder.java
+++ b/services/core/java/com/android/server/wm/DisplayAreaPolicyBuilder.java
@@ -38,6 +38,7 @@
 import android.window.DisplayAreaOrganizer;
 import android.window.WindowContainerToken;
 
+import com.android.internal.annotations.Keep;
 import com.android.internal.annotations.VisibleForTesting;
 import com.android.internal.protolog.common.ProtoLog;
 import com.android.server.policy.WindowManagerPolicy;
@@ -142,6 +143,7 @@
  * the window to the corresponding {@link DisplayArea.Tokens} under the returned root
  * {@link RootDisplayArea}.
  */
+@Keep
 class DisplayAreaPolicyBuilder {
 
     @Nullable private HierarchyBuilder mRootHierarchyBuilder;