[DevTools] Account for synthetic events in deepElementFromPoint()

third_party/WebKit/Source/devtools/front_end/dom_extension/DOMExtension.js

 /*
  * Copyright (C) 2007 Apple Inc.  All rights reserved.
  * Copyright (C) 2012 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  *
  * 1.  Redistributions of source code must retain the above copyright
  *     notice, this list of conditions and the following disclaimer.
@@ skipping 739 matching lines @@
   }
 
   this.textContent = text;
   return false;
 };
 
 /**
  * @return {?Node}
  */
 Event.prototype.deepElementFromPoint = function() {
+  // Some synthetic events have zero coordinates which lead to a wrong element. Better return nothing in this case.
+  if (!this.which && !this.pageX && !this.pageY && !this.clientX && !this.clientY && !this.movementX && !this.movementY)
+    return null;
   var root = this.target && this.target.getComponentRoot();
   return root ? root.deepElementFromPoint(this.pageX, this.pageY) : null;
 };
 
 /**
  * @param {number} x
  * @param {number} y
  * @return {?Node}
  */
 Document.prototype.deepElementFromPoint = function(x, y) {
@@ skipping 50 matching lines @@
   return event.keyCode !== 229 && event.key === 'Enter';
 }
 
 /**
  * @param {!Event} event
  * @return {boolean}
  */
 function isEscKey(event) {
   return event.keyCode === 27;
 }