Helper to support getContext options map analysis.

tools/dom/src/native_DOMImplementation.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.
 
 part of html;
 
 class _Utils {
   static double dateTimeToDouble(DateTime dateTime) =>
       dateTime.millisecondsSinceEpoch.toDouble();
   static DateTime doubleToDateTime(double dateTime) {
@@ skipping 13 matching lines @@
     result.setRange(0, length, list);
     return result;
   }
 
   static List convertMapToList(Map map) {
     List result = [];
     map.forEach((k, v) => result.addAll([k, v]));
     return result;
   }
 
+  static int convertCanvasElementGetContextMap(Map map) {
+    int result = 0;
+    if (map['alpha'] == true) result |= 0x01;
+    if (map['depth'] == true) result |= 0x02;
+    if (map['stencil'] == true) result |= 0x4;
+    if (map['antialias'] == true) result |= 0x08;
+    if (map['premultipliedAlpha'] == true) result |= 0x10;
+    if (map['preserveDrawingBuffer'] == true) result |= 0x20;
+
+    return result;
+  }
+
   static void populateMap(Map result, List list) {
     for (int i = 0; i < list.length; i += 2) {
       result[list[i]] = list[i + 1];
     }
   }
 
   static bool isMap(obj) => obj is Map;
 
   static Map createMap() => {};
 
@@ skipping 78 matching lines @@
 
 get _printClosure => (s) {
   try {
     window.console.log(s);
   } catch (_) {
     _Utils.print(s);
   }
 };
 
 final _forwardingPrintClosure = _Utils.forwardingPrint;