Fix two typos in Observatory.

runtime/observatory/lib/src/elements/debugger.dart

 // Copyright (c) 2014, 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 debugger_page_element;
 
 import 'dart:async';
 import 'dart:html';
 import 'observatory_element.dart';
 import 'package:observatory/app.dart';
@@ skipping 1766 matching lines @@
     int fixedHeight = navbarHeight + splitterHeight + cmdHeight;
     int available = windowHeight - fixedHeight;
     int stackHeight = available ~/ 1.6;
     stackDiv.style.setProperty('height', '${stackHeight}px');
   }
 
   @override
   void detached() {
     debugger.isolate = null;
     _resizeSubscription.cancel();
-    _resizeSubscrption = null;
+    _resizeSubscription = null;
     cancelFutureSubscription(_isolateSubscriptionFuture);
     _isolateSubscriptionFuture = null;
     cancelFutureSubscription(_debugSubscriptionFuture);
     _debugSubscriptionFuture = null;
     cancelFutureSubscription(_stdoutSubscriptionFuture);
     _stdoutSubscriptionFuture = null;
     cancelFutureSubscription(_stderrSubscriptionFuture);
     _stderrSubscriptionFuture = null;
     cancelFutureSubscription(_logSubscriptionFuture);
     _logSubscriptionFuture = null;
@@ skipping 561 matching lines @@
         }
       });
   }
 
   void focus() {
     $['textBox'].focus();
   }
 
   DebuggerInputElement.created() : super.created();
 }