Allow split position constants to be used in launcher.

- Added SplitScreenConstants class and added this class to the exported files to allow exporting window manager constants and methods to the launcher.

Bug: 198438631
Test: manual
Change-Id: I7c5649449389413d1435798c3e757103c4ced038
Merged-In: I7c5649449389413d1435798c3e757103c4ced038
(cherry picked from commit a191eb7e3c099a3ffde25d59d5203f2b3e4bdfa2)
diff --git a/libs/WindowManager/Shell/Android.bp b/libs/WindowManager/Shell/Android.bp
index 8e3d726..cdff585 100644
--- a/libs/WindowManager/Shell/Android.bp
+++ b/libs/WindowManager/Shell/Android.bp
@@ -43,6 +43,7 @@
     name: "wm_shell_util-sources",
     srcs: [
         "src/com/android/wm/shell/util/**/*.java",
+        "src/com/android/wm/shell/common/split/SplitScreenConstants.java"
     ],
     path: "src",
 }