Simplify the check for isDefaultPrevented.

src/event.js

@@ -602,10 +602,8 @@ jQuery.Event = function( src ) {
 		this.type = src.type;
 		// Events bubbling up the document may have been marked as prevented
 		// by a handler lower down the tree; reflect the correct value.
-		this.isDefaultPrevented =
-			(src.defaultPrevented===true ? true :
-			 src.getPreventDefault ? src.getPreventDefault() :
-			 src.returnValue===false) ? returnTrue : returnFalse;
+		this.isDefaultPrevented = (src.defaultPrevented || src.returnValue === false || 
+			src.getPreventDefault && src.getPreventDefault()) ? returnTrue : returnFalse;
 	// Event type
 	} else {
 		this.type = src;