Accessibility to toggle multiwindow mode

Encapsulating the logic to toggle multiwindow mode from recents,
and plumbing it through to accessibility global actions. Sending
accessibility events when windows bounds change. Exposing the
dock divider window type to accessibility services.

Bug: 27250995
Change-Id: Ib7491f1f853dc7f01bf5c5a4ac1f914f55d0608a
diff --git a/packages/SystemUI/src/com/android/systemui/statusbar/tv/TvStatusBar.java b/packages/SystemUI/src/com/android/systemui/statusbar/tv/TvStatusBar.java
index 110258c..0ed6ef8 100644
--- a/packages/SystemUI/src/com/android/systemui/statusbar/tv/TvStatusBar.java
+++ b/packages/SystemUI/src/com/android/systemui/statusbar/tv/TvStatusBar.java
@@ -116,6 +116,11 @@
     }
 
     @Override
+    protected boolean toggleSplitScreenMode() {
+        return false;
+    }
+
+    @Override
     public void maybeEscalateHeadsUp() {
     }