Suppress stream subscription error

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 1688 matching lines @@
     debugger.input = $['commandline'];
     debugger.input.debugger = debugger;
     debugger.init();
 
     _isolateSubscriptionFuture =
         app.vm.listenEventStream(VM.kIsolateStream, debugger.onEvent);
     _debugSubscriptionFuture =
         app.vm.listenEventStream(VM.kDebugStream, debugger.onEvent);
     _stdoutSubscriptionFuture =
         app.vm.listenEventStream(VM.kStdoutStream, debugger.onStdout);
+    if (_stdoutSubscriptionFuture != null) {
+      // TODO(turnidge): How do we want to handle this in general?
+      _stdoutSubscriptionFuture.catchError((e, st) {
+        Logger.root.info('Failed to subscribe to stdout: $e\n$st\n');
+      });
+    }
     _stderrSubscriptionFuture =
         app.vm.listenEventStream(VM.kStderrStream, debugger.onStderr);
+    if (_stderrSubscriptionFuture != null) {
+      // TODO(turnidge): How do we want to handle this in general?
+      _stderrSubscriptionFuture.catchError((e, st) {
+        Logger.root.info('Failed to subscribe to stderr: $e\n$st\n');
+      });
+    }
     _logSubscriptionFuture =
         app.vm.listenEventStream(Isolate.kLoggingStream, debugger.onEvent);
     // Turn on the periodic poll timer for this page.
     pollPeriod = const Duration(milliseconds:100);
 
     onClick.listen((event) {
       // Random clicks should focus on the text box.  If the user selects
       // a range, don't interfere.
       var selection = window.getSelection();
       if (selection == null ||
@@ skipping 584 matching lines @@
         }
       });
   }
 
   void focus() {
     $['textBox'].focus();
   }
 
   DebuggerInputElement.created() : super.created();
 }