Use dart:html prefixes (e.g. webkitAudioNode) on other browsers

pkg/dev_compiler/tool/input_sdk/private/ddc_runtime/classes.dart

 // Copyright (c) 2015, 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.
 
 /// This library defines the operations that define and manipulate Dart
 /// classes.  Included in this are:
 ///   - Generics
 ///   - Class metadata
 ///   - Extension methods
 ///
@@ skipping 483 matching lines @@
 
 /// Link the extension to the type it's extending as a base class.
 setBaseClass(derived, base) {
   JS('', '#.prototype.__proto__ = #.prototype', derived, base);
   // We use __proto__ to track the superclass hierarchy (see isSubtype).
   JS('', '#.__proto__ = #', derived, base);
 }
 
 /// Like [setBaseClass] but for generic extension types, e.g. `JSArray<E>`
 setExtensionBaseClass(derived, base) {
-  // Mark the generic type as an extension type.
-  JS('', '#.prototype[#] = #', derived, _extensionType, derived);
-  // Link the prototype objects
-  JS('', '#.prototype.__proto__ = #.prototype', derived, base);
+  // Mark the generic type as an extension type and link the prototype objects
+  return JS('', '''(() => {
+    if ($base) {
+      $derived.prototype[$_extensionType] = $derived;
+      $derived.prototype.__proto__ = $base.prototype
+    }
+})()''');
 }
 
 /// Given a special constructor function that creates a function instances,
 /// and a class with a `call` method, merge them so the constructor function
 /// will have the correct methods and prototype.
 ///
 /// For example:
 ///
 ///     lib.Foo = dart.callableClass(
 ///         function Foo { function call(...args) { ... } ... return call; },
@@ skipping 17 matching lines @@
 ///
 /// The constructor
 defineNamedConstructorCallable(clazz, name, ctor) => JS(
     '',
     '''(() => {
   ctor.prototype = $clazz.prototype;
   // Use defineProperty so we don't hit a property defined on Function,
   // like `caller` and `arguments`.
   $defineProperty($clazz, $name, { value: ctor, configurable: true });
 })()''');