Compile chrome://settings, part 9: yet another final battle

ui/webui/resources/js/cr/ui/touch_handler.js

Index: ui/webui/resources/js/cr/ui/touch_handler.js
diff --git a/ui/webui/resources/js/cr/ui/touch_handler.js b/ui/webui/resources/js/cr/ui/touch_handler.js
index acc12afe1f5df22177c23106e0bc89487927cace..315fef0188f290f8fc5eea2854bfd32ce91ec8e5 100644
--- a/ui/webui/resources/js/cr/ui/touch_handler.js
+++ b/ui/webui/resources/js/cr/ui/touch_handler.js
@@ -788,6 +788,8 @@ cr.define('cr.ui', function() {
       this.disableTap_ = true;
 
       // Dispatch to the LONG_PRESS
+      assert(typeof this.startTouchX_ == 'number');
+      assert(typeof this.startTouchY_ == 'number');
       this.dispatchEventXY_(TouchHandler.EventType.LONG_PRESS, this.element_,
           /** @type {number} */(this.startTouchX_),
           /** @type {number} */(this.startTouchY_));