Move system property for Window Extensions to WindowManager

So that it can be reference outside of the wm/ directory, and used in
CTS.

Bug: 235797785
Test: refactor only
Change-Id: I837ecf978bb42b7da45dd5afdc7d7de0b4d2914e

core/api/test-current.txt

@@ -3263,6 +3263,7 @@ package android.view {
 
   public interface WindowManager extends android.view.ViewManager {
     method public default int getDisplayImePolicy(int);
+    method public static boolean hasWindowExtensionsEnabled();
     method public default void holdLock(android.os.IBinder, int);
     method public default boolean isGlobalKey(int);
     method public default boolean isTaskSnapshotSupported();

core/java/android/view/WindowManager.java

@@ -108,6 +108,7 @@ import android.os.Bundle;
 import android.os.IBinder;
 import android.os.Parcel;
 import android.os.Parcelable;
+import android.os.SystemProperties;
 import android.text.TextUtils;
 import android.util.Log;
 import android.util.proto.ProtoOutputStream;
@@ -1103,6 +1104,26 @@ public interface WindowManager extends ViewManager {
      */
     public static final String PARCEL_KEY_SHORTCUTS_ARRAY = "shortcuts_array";
 
+    /**
+     * Whether the device supports the WindowManager Extensions.
+     * OEMs can enable this by having their device config to inherit window_extensions.mk, such as:
+     * <pre>
+     * $(call inherit-product, $(SRC_TARGET_DIR)/product/window_extensions.mk)
+     * </pre>
+     * @hide
+     */
+    boolean WINDOW_EXTENSIONS_ENABLED =
+            SystemProperties.getBoolean("persist.wm.extensions.enabled", false);
+
+    /**
+     * @see #WINDOW_EXTENSIONS_ENABLED
+     * @hide
+     */
+    @TestApi
+    static boolean hasWindowExtensionsEnabled() {
+        return WINDOW_EXTENSIONS_ENABLED;
+    }
+
     /**
      * Application-level
      * {@link android.content.pm.PackageManager.Property PackageManager.Property}

services/core/java/com/android/server/wm/ActivityRecord.java

@@ -2149,7 +2149,7 @@ final class ActivityRecord extends WindowToken implements WindowManagerService.A
 
         boolean appActivityEmbeddingEnabled = false;
         try {
-            appActivityEmbeddingEnabled = WindowManagerService.sWindowExtensionsEnabled
+            appActivityEmbeddingEnabled = WindowManager.hasWindowExtensionsEnabled()
                     && mAtmService.mContext.getPackageManager()
                             .getProperty(PROPERTY_ACTIVITY_EMBEDDING_SPLITS_ENABLED, packageName)
                             .getBoolean();

services/core/java/com/android/server/wm/WindowManagerService.java

@@ -441,16 +441,6 @@ public class WindowManagerService extends IWindowManager.Stub
     static final boolean ENABLE_FIXED_ROTATION_TRANSFORM =
             SystemProperties.getBoolean("persist.wm.fixed_rotation_transform", true);
 
-    /**
-     * Whether the device supports the WindowManager Extensions.
-     * OEMs can enable this by having their device config to inherit window_extensions.mk, such as:
-     * <pre>
-     * $(call inherit-product, $(SRC_TARGET_DIR)/product/window_extensions.mk)
-     * </pre>
-     */
-    static final boolean sWindowExtensionsEnabled =
-            SystemProperties.getBoolean("persist.wm.extensions.enabled", false);
-
     // Enums for animation scale update types.
     @Retention(RetentionPolicy.SOURCE)
     @IntDef({WINDOW_ANIMATION_SCALE, TRANSITION_ANIMATION_SCALE, ANIMATION_DURATION_SCALE})