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

runtime/observatory/lib/src/app/page.dart

Index: runtime/observatory/lib/src/app/page.dart
diff --git a/runtime/observatory/lib/src/app/page.dart b/runtime/observatory/lib/src/app/page.dart
index 7457b1d3828278ed168587fedbb028e3bea9cc55..b16cc3036e17f61f6885ad0ca2515abc69190f5e 100644
--- a/runtime/observatory/lib/src/app/page.dart
+++ b/runtime/observatory/lib/src/app/page.dart
@@ -4,6 +4,12 @@
 
 part of app;
 
+class IsolateNotFound implements Exception {
+  String isolateId;
+  IsolateNotFound(this.isolateId);
+  String toString() => "IsolateNotFound: $isolateId";
+}
+
 /// A [Page] controls the user interface of Observatory. At any given time
 /// one page will be the current page. Pages are registered at startup.
 /// When the user navigates within the application, each page is asked if it
@@ -59,11 +65,13 @@ class SimplePage extends Page {
   }
 
   Future<Isolate> getIsolate(Uri uri) {
-    return app.vm.getIsolate(uri.queryParameters['isolateId'])
-      .catchError((e, stack) {
-        Logger.root.severe('$path visit error: $e\n$stack');
-        return e;
-      });
+    var isolateId = uri.queryParameters['isolateId'];
+    return app.vm.getIsolate(isolateId).then((isolate) {

[rmacnak, 2015/04/23 18:32:19]

Probably push this into the service library.

[turnidge, 2015/05/01 17:23:55]

I'm working on this currently in another CL.

+      if (isolate == null) {
+        throw new IsolateNotFound(isolateId);
+      }
+      return isolate;
+    });
   }
 
   bool canVisit(Uri uri) => uri.path == path;
@@ -292,8 +300,26 @@ class VMConnectPage extends Page {
     assert(canVisit(uri));
   }
 
-  // TODO(turnidge): Update this to not have the trailing slash.
-  bool canVisit(Uri uri) => uri.path.startsWith('vm-connect/');
+  bool canVisit(Uri uri) => uri.path.startsWith('vm-connect');
+}
+
+class IsolateReconnectPage extends Page {
+  IsolateReconnectPage(app) : super(app);
+
+  void onInstall() {
+    if (element == null) {
+      element = new Element.tag('isolate-reconnect');
+    }
+    assert(element != null);
+  }
+
+  void _visit(Uri uri) {
+    app.vm.reload();
+    assert(element != null);
+    assert(canVisit(uri));
+  }
+
+  bool canVisit(Uri uri) => uri.path.startsWith('isolate-reconnect');
 }
 
 class MetricsPage extends Page {