dart:js_util - fix spelling

sdk/lib/js_util/dartium/js_util_dartium.dart

 // Copyright (c) 2016, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 /// Utility methods to efficiently manipulate typed JSInterop objects in cases
 /// where the name to call is not known at runtime. You should only use these
 /// methods when the same effect cannot be achieved with @JS annotations.
 /// These methods would be extension methods on JSObject if Dart supported
 /// extension methods.
 library dart.js_util;
 
 import 'dart:js';
 
-/// WARNING: performance of this method is much worse than other uitil
+/// WARNING: performance of this method is much worse than other util
 /// methods in this library. Only use this method as a last resort.
 ///
 /// Recursively converts a JSON-like collection of Dart objects to a
 /// collection of JavaScript objects and returns a [JsObject] proxy to it.
 ///
 /// [object] must be a [Map] or [Iterable], the contents of which are also
 /// converted. Maps and Iterables are copied to a new JavaScript object.
-/// Primitives and other transferrable values are directly converted to their
+/// Primitives and other transferable values are directly converted to their
 /// JavaScript type, and all other objects are proxied.
 jsify(object) {
   if ((object is! Map) && (object is! Iterable)) {
     throw new ArgumentError("object must be a Map or Iterable");
   }
   return JsNative.jsify(object);
 }
 
 JSObject newObject() => JsNative.newObject();
 
 hasProperty(JSObject o, name) => JsNative.hasProperty(o, name);
 getProperty(JSObject o, name) => JsNative.getProperty(o, name);
 setProperty(JSObject o, name, value) => JsNative.setProperty(o, name, value);
 callMethod(JSObject o, String method, List args) => JsNative.callMethod(o, method, args);
 instanceof(JSObject o, Function type) => JsNative.instanceof(o, type);
 callConstructor(JSObject constructor, List args) => JsNative.callConstructor(constructor, args);