Use onClosed instead of onError in the WebSocket classes.

runtime/bin/websocket.dart

Index: runtime/bin/websocket.dart
diff --git a/runtime/bin/websocket.dart b/runtime/bin/websocket.dart
index c11a569497e23d1709a0dbfcfbce03a4082ff912..e7375da3baf7c8c140738047b652a83ef31f5f60 100644
--- a/runtime/bin/websocket.dart
+++ b/runtime/bin/websocket.dart
@@ -54,12 +54,6 @@ interface WebSocketConnection extends Hashable {
   void set onClosed(void callback(int status, String reason));
 
   /**
-   * Sets the callback to be called when the web socket connection
-   * encountered an error.
-   */
-  void set onError(void callback(e));
-
-  /**
    * Sends a message. The [message] must be a [:String:] a
    * [:List<int>:] or [:null:].
    */
@@ -129,12 +123,6 @@ interface WebSocketClientConnection
   void set onNoUpgrade(void callback(HttpClientResponse response));
 
   /**
-   * Sets the callback to be called when the web socket connection
-   * encountered an error.
-   */
-  void set onError(void callback(e));
-
-  /**
    * Sends a message. The [message] must be a [:String:] or a
    * [:List<int>:]. To send an empty message use either an empty
    * [:String:] or an empty [:List<int>:]. [:null:] cannot be used.