When attempting to navigate to a page for an isolate that doesn't exist, offer to

runtime/observatory/lib/src/app/location_manager.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.
 
 part of app;
 
 class LocationManager extends Observable {
   final _defaultPath = '/vm';
 
   final ObservatoryApplication _app;
@@ skipping 61 matching lines @@
     _uri = Uri.parse(url);
   }
 
   /// Add [url] to the browser history.
   _addToBrowserHistory(String url) {
     window.history.pushState(url, document.title, url);
   }
 
   /// Notify the current page that something has changed.
   _visit() {
-    _app._visit(_uri, internalArguments);
+    runZoned(() => _app._visit(_uri, internalArguments),
+             onError: (e, st) {
+      if (e is IsolateNotFound) {
+        var newPath = _app.vm == null ? '/vm-connect' : '/isolate-reconnect';
+        var parameters = {};
+        parameters.addAll(_uri.queryParameters);
+        parameters['originalPath'] = _uri.path;
+        parameters['originalIsolateId'] = parameters['isolateId'];
+        var generatedUri = new Uri(path: newPath, queryParameters: parameters);
+        go(makeLink(generatedUri.toString()), true);
+        return;
+      }
+      throw e;
+    });
   }
 
   /// Navigate to [url].
   void go(String url, [bool addToBrowserHistory = true]) {
-    if ((url != makeLink('/vm-connect/')) && _app.vm == null) {
+    if ((url != makeLink('/vm-connect')) && _app.vm == null) {
       if (!window.confirm('Connection with VM has been lost. '
                           'Proceeding will lose current page.')) {
         return;
       }
       url = makeLink('/vm-connect/');
     }
     if (addToBrowserHistory) {
       _addToBrowserHistory(url);
     }
     _updateApplicationLocation(url);
     _visit();
   }
 
   /// Starting with the current uri path and queryParameters, update
   /// queryParameters present in [updateParameters], then generate a new uri
   /// and navigate to that.
-  goParameter(Map updatedParameters, [bool addToBrowserHistory = true]) {
+  goReplacingParameters(Map updatedParameters, [bool addToBrowserHistory = true]) {
+    go(makeLinkReplacingParameter(updatedParameters), addToBrowserHistory);
+  }
+
+  makeLinkReplacingParameters(Map updatedParameters) {
     var parameters = new Map.from(_uri.queryParameters);
     updatedParameters.forEach((k, v) {
       parameters[k] = v;
     });
     // Ensure path starts with a slash.
     var path = uri.path.startsWith('/') ? uri.path : '/${uri.path}';
     var generatedUri = new Uri(path: path, queryParameters: parameters);
-    go(makeLink(generatedUri.toString()), addToBrowserHistory);
+    return makeLink(generatedUri.toString());
+  }
+
+  goForwardingParameters(String newPath, [bool addToBrowserHistory = true]) {
+    go(makeLinkForwardingParameters(newPath), addToBrowserHistory);
+  }
+
+  makeLinkForwardingParameters(String newPath) {
+    var parameters = _uri.queryParameters;
+    var generatedUri = new Uri(path: newPath, queryParameters: parameters);
+    return makeLink(generatedUri.toString());
   }
 
   /// Utility event handler when clicking on application url link.
   void onGoto(MouseEvent event) {
     if ((event.button > 0) ||
         event.metaKey      ||
         event.ctrlKey      ||
         event.shiftKey     ||
         event.altKey) {
       // Mouse event is not a left-click OR
       // mouse event is a left-click with a modifier key:
       // let browser handle.
       return;
     }
     event.preventDefault();
     var target = event.target;
     go(target.attributes['href']);
   }
 }