Adding window_extensions.mk am: 0df807eab6

Original change: https://googleplex-android-review.googlesource.com/c/platform/build/+/20271257

Change-Id: I5f3cc3713478c55e499593ed982a17cee5fb7ea7
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>

target/product/window_extensions.mk

@@ -0,0 +1,24 @@
+#
+# Copyright (C) 2022 The Android Open Source Project
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+#
+
+# /system_ext packages
+PRODUCT_PACKAGES += \
+    androidx.window.extensions \
+    androidx.window.sidecar
+
+# properties
+PRODUCT_PRODUCT_PROPERTIES += \
+    persist.wm.extensions.enabled=true