Keep track of closing socket, in WebSocket, so we don't write once the socket is closed.

tests/standalone/io/web_socket_test.dart

 // Copyright (c) 2013, 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.
 //
 // VMOptions=
 // VMOptions=--short_socket_read
 // VMOptions=--short_socket_write
 // VMOptions=--short_socket_read --short_socket_write
 
 import "dart:async";
@@ skipping 146 matching lines @@
             } else if (event is CloseEvent) {
               server.close();
             }
           });
           webSocket.send(originalMessage);
         });
     });
   }
 
 
+  void testDoubleCloseClient() {
+    createServer().then((server) {
+      server.transform(new WebSocketTransformer()).listen((webSocket) {
+        webSocket.listen((event) {
+          if (event is CloseEvent) {
+            webSocket.close();
+          }
+        });
+      });
+
+      createClient(server.port).then((webSocket) {
+          webSocket.listen((event) {
+            if (event is CloseEvent) {
+              webSocket.close();
+            }
+          });
+          webSocket.close();
+        });
+    });
+  }
+
+
+  void testDoubleCloseServer() {
+    createServer().then((server) {
+      server.transform(new WebSocketTransformer()).listen((webSocket) {
+        webSocket.listen((event) {
+          if (event is CloseEvent) {
+            webSocket.close();
+          }
+        });
+        webSocket.close();
+      });
+
+      createClient(server.port).then((webSocket) {
+          webSocket.listen((event) {
+            if (event is CloseEvent) {
+              webSocket.close();
+            }
+          });
+        });
+    });
+  }
+
+
   void testNoUpgrade() {
     createServer().then((server) {
       // Create a server which always responds with NOT_FOUND.
       server.listen((request) {
         request.response.statusCode = HttpStatus.NOT_FOUND;
         request.response.close();
       });
 
       createClient(server.port).catchError((error) {
         server.close();
@@ skipping 95 matching lines @@
     testRequestResponseClientCloses(2, 3001, null);
     testRequestResponseClientCloses(2, 3002, "Got tired");
     testRequestResponseServerCloses(2, null, null);
     testRequestResponseServerCloses(2, 3001, null);
     testRequestResponseServerCloses(2, 3002, "Got tired");
     testMessageLength(125);
     testMessageLength(126);
     testMessageLength(127);
     testMessageLength(65535);
     testMessageLength(65536);
+    testDoubleCloseClient();
+    testDoubleCloseServer();
     testNoUpgrade();
     testUsePOST();
     testW3CInterface(10, 3002, "Got tired");
   }
 }
 
 
 void initializeSSL() {
   var testPkcertDatabase =
       new Path(new Options().script).directoryPath.append("pkcert/");
   SecureSocket.initialize(database: testPkcertDatabase.toNativePath(),
                           password: "dartdart");
 }
 
 
 main() {
   new SecurityConfiguration(secure: false).runTests();
   initializeSSL();
   new SecurityConfiguration(secure: true).runTests();
 }