cleanup check for sourceCapabilities

src/standard/gestures.html

@@ -41,23 +41,19 @@
   // Check for touch-only devices
   var IS_TOUCH_ONLY = navigator.userAgent.match(/iP(?:[oa]d|hone)|Android/);
 
-  // Check for sourceCapabilities, used to distinguish synthetic events
-  var HAS_SOURCE_CAPS = 'sourceCapabilities' in UIEvent.prototype;
-
   // touch will make synthetic mouse events
   // `preventDefault` on touchend will cancel them,
   // but this breaks `<input>` focus and link clicks
   // disable mouse handlers for MOUSE_TIMEOUT ms after
   // a touchend to ignore synthetic mouse events
   var mouseCanceller = function(mouseEvent) {
-    if (HAS_SOURCE_CAPS) {
-      // if mouseEvent did not come from a device that fires touch events,
-      // it was made by a real mouse and should be counted
-      // http://wicg.github.io/InputDeviceCapabilities/#dom-inputdevicecapabilities-firestouchevents
-      var sc = mouseEvent.sourceCapabilities;
-      if (sc && !sc.firesTouchEvents) {
-        return;
-      }
+    // Check for sourceCapabilities, used to distinguish synthetic events
+    // if mouseEvent did not come from a device that fires touch events,
+    // it was made by a real mouse and should be counted
+    // http://wicg.github.io/InputDeviceCapabilities/#dom-inputdevicecapabilities-firestouchevents
+    var sc = mouseEvent.sourceCapabilities;
+    if (sc && !sc.firesTouchEvents) {
+      return;
     }
     // skip synthetic mouse events
     mouseEvent[HANDLED_OBJ] = {skip: true};