Fix more warnings for dart:html.

sdk/lib/html/html_common/conversions.dart

 // Copyright (c) 2012, 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.
 
 
 // Conversions for IDBKey.
 //
 // Per http://www.w3.org/TR/IndexedDB/#key-construct
 //
 // "A value is said to be a valid key if it is one of the following types: Array
@@ skipping 286 matching lines @@
 // Conversions for ContextAttributes.
 //
 // On Firefox, the returned ContextAttributes is a plain object.
 class _TypedContextAttributes implements gl.ContextAttributes {
   bool alpha;
   bool antialias;
   bool depth;
   bool premultipliedAlpha;
   bool preserveDrawingBuffer;
   bool stencil;
+  bool failIfMajorPerformanceCaveat;
 
   _TypedContextAttributes(this.alpha, this.antialias, this.depth,
       this.premultipliedAlpha, this.preserveDrawingBuffer, this.stencil);
 }
 
 gl.ContextAttributes convertNativeToDart_ContextAttributes(
     nativeContextAttributes) {
   if (nativeContextAttributes is gl.ContextAttributes) {
     return nativeContextAttributes;
   }
@@ skipping 82 matching lines @@
 const String _serializedScriptValue =
     'num|String|bool|'
     'JSExtendableArray|=Object|'
     'Blob|File|NativeByteBuffer|NativeTypedData'
     // TODO(sra): Add Date, RegExp.
     ;
 const annotation_Creates_SerializedScriptValue =
     const Creates(_serializedScriptValue);
 const annotation_Returns_SerializedScriptValue =
     const Returns(_serializedScriptValue);