Import FileAPI tests from web-platform-tests

LayoutTests/imported/web-platform-tests/shadow-dom/testcommon.js

 // Copyright 2012 Google Inc. All Rights Reserved.
 
 /*
 Distributed under both the W3C Test Suite License [1] and the W3C
 3-clause BSD License [2]. To contribute to a W3C Test Suite, see the
 policies and contribution forms [3].
 
 [1] http://www.w3.org/Consortium/Legal/2008/04-testsuite-license
 [2] http://www.w3.org/Consortium/Legal/2008/03-bsd-license
 [3] http://www.w3.org/2004/10/27-testcases
@@ skipping 162 matching lines @@
             e.parentNode.removeChild(e);
         });
     }
 }
 
 function unit(f) {
     return function () {
         var ctx = newContext();
         try {
             f(ctx);
-        } catch(e) {
-            console.log(e.getMessage());
         } finally {
             cleanContext(ctx);
         }
     }
 }
 
 function step_unit(f, ctx, t) {
     return function () {
         var done = false;
         try {
@@ skipping 69 matching lines @@
 }
 
 //FIXME This call of initKeyboardEvent works for WebKit-only.
 //See https://bugs.webkit.org/show_bug.cgi?id=16735
 // and https://bugs.webkit.org/show_bug.cgi?id=13368. Add check for browser here
 function fireKeyboardEvent(doc, element, key) {
     var event = doc.createEvent('KeyboardEvent');
     event.initKeyboardEvent("keydown", true, true, doc.defaultView, key, 0, false, false, false, false);
     element.dispatchEvent(event);
 }