Adding support checks for ApplicationCache.

sdk/lib/html/html_common/metadata.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.
 
 library metadata;
 
 /**
  * An annotation used to mark a feature as only being supported by a subset
  * of the browsers that Dart supports by default.
  *
  * If an API is not annotated with [SupportedBrowser] then it is assumed to
  * work on all browsers Dart supports.
  */
 class SupportedBrowser {
   static const String CHROME = "Chrome";
   static const String FIREFOX = "Firefox";
   static const String IE = "Internet Explorer";
+  static const String OPERA = "Opera";
   static const String SAFARI = "Safari";
 
   /// The name of the browser.
   final String browserName;
   /// The minimum version of the browser that supports the feature, or null
   /// if supported on all versions.
   final String minimumVersion;
 
   const SupportedBrowser(this.browserName, [this.minimumVersion]);
 }
 
 
 /**
  * An annotation used to mark an API as being experimental.
  *
  * An API is considered to be experimental if it is still going through the
  * process of stabilizing and is subject to change or removal.
  *
  * See also:
  *
  * * [W3C recommendation](http://en.wikipedia.org/wiki/W3C_recommendation)
  */
 class Experimental {
   const Experimental();
 }