Rework error handling in the service protocol and in Observatory.

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 64 matching lines @@
   /// 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() {
     runZoned(() => _app._visit(_uri, internalArguments),
              onError: (e, st) {
       if (e is IsolateNotFound) {
-        var newPath = _app.vm == null ? '/vm-connect' : '/isolate-reconnect';
+        var newPath = ((_app.vm == null || _app.vm.isDisconnected)
+                       ? '/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;
+      // Surface any uncaught exceptions.
+      _app.handleException(e, st);
     });
   }
 
   /// 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 || _app.vm.isDisconnected)) {
       if (!window.confirm('Connection with VM has been lost. '
                           'Proceeding will lose current page.')) {
         return;
       }
-      url = makeLink('/vm-connect/');
+      url = makeLink('/vm-connect');
     }
+
+    if (url == makeLink('/vm-connect')) {
+      // When we go to the vm-connect page, drop all notifications.
+      _app.notifications.clear();
+    }
+
     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.
@@ skipping 34 matching lines @@
       // let browser handle.
       return;
     }
     event.preventDefault();
     // 'currentTarget' is the dom element that would process the event.
     // If we use 'target' we might get an <em> element or somesuch.
     var target = event.currentTarget;
     go(target.attributes['href']);
   }
 }