Adding support checks for WebSocket.

sdk/lib/html/dartium/html_dartium.dart

Index: sdk/lib/html/dartium/html_dartium.dart
diff --git a/sdk/lib/html/dartium/html_dartium.dart b/sdk/lib/html/dartium/html_dartium.dart
index 619bc74f9ad629167624745b98d3ef1371a23d36..2cbde772bb0464dcd76e3f674b0a07d43508e260 100644
--- a/sdk/lib/html/dartium/html_dartium.dart
+++ b/sdk/lib/html/dartium/html_dartium.dart
@@ -25433,6 +25433,10 @@ class WebKitNamedFlow extends EventTarget {
 
 
 /// @domName WebSocket
+@SupportedBrowser(SupportedBrowser.CHROME)
+@SupportedBrowser(SupportedBrowser.FIREFOX)
+@SupportedBrowser(SupportedBrowser.IE, '10')
+@SupportedBrowser(SupportedBrowser.SAFARI)
 class WebSocket extends EventTarget {
   WebSocket.internal() : super.internal();
 
@@ -25440,6 +25444,11 @@ class WebSocket extends EventTarget {
   factory WebSocket(String url) => WebSocket._create(url);
   static WebSocket _create(String url) native "WebSocket_constructor_Callback";
 
+  /**
+   * Checks if this type is supported on the current platform
+   */
+  static bool get supported => true;
+
   /// @domName EventTarget.addEventListener, EventTarget.removeEventListener, EventTarget.dispatchEvent; @docsEditable true
   WebSocketEvents get on =>
     new WebSocketEvents(this);