Remove more keyboard usability related code

BUG=414766

Review URL: https://codereview.chromium.org/587243004

Cr-Commit-Position: refs/heads/master@{#296250}
diff --git a/ash/root_window_controller.h b/ash/root_window_controller.h
index 014aadc..bb047e6 100644
--- a/ash/root_window_controller.h
+++ b/ash/root_window_controller.h
@@ -242,8 +242,7 @@
   explicit RootWindowController(AshWindowTreeHost* host);
   enum RootWindowType {
     PRIMARY,
-    SECONDARY,
-    VIRTUAL_KEYBOARD
+    SECONDARY
   };
 
   // Initializes the RootWindowController.  |is_primary| is true if