Give Divider back its touch-region

Divider used to have a touch-region that allowed apps
to receive touch events that would normally overlap the
divider window as long as they weren't in the center.

Re-introduce this by allowing windowless windows to
pass through a touch-region. This region is always
constrained to the window size to prevent security issues.

Bug: 154840035
Test: Enter split and observe touch events away from
      center of divider.
Change-Id: I85310c78beda7bd5574df78e2a83462e965d1154
diff --git a/services/core/java/com/android/server/wm/Session.java b/services/core/java/com/android/server/wm/Session.java
index 56147f2..bf20cb9 100644
--- a/services/core/java/com/android/server/wm/Session.java
+++ b/services/core/java/com/android/server/wm/Session.java
@@ -679,10 +679,10 @@
 
     @Override
     public void updateInputChannel(IBinder channelToken, int displayId, SurfaceControl surface,
-            int flags) {
+            int flags, Region region) {
         final long identity = Binder.clearCallingIdentity();
         try {
-            mService.updateInputChannel(channelToken, displayId, surface, flags);
+            mService.updateInputChannel(channelToken, displayId, surface, flags, region);
         } finally {
             Binder.restoreCallingIdentity(identity);
         }