Add isolate tag-profile and better handling of errors

runtime/bin/vmservice/client/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;
 
 /// The LocationManager class observes and parses the hash ('#') portion of the
 /// URL in window.location. The text after the '#' is used as the request
 /// string for the VM service.
 class LocationManager extends Observable {
   static const String defaultHash = '#/vm';
 
   ObservatoryApplication _app;
   @observable String currentHash = '';
 
   void init() {
     window.onHashChange.listen((event) {
-      if (setDefaultHash()) {
-        // We just triggered another onHashChange event.
-        return;
-      }
       // Request the current anchor.
       requestCurrentHash();
     });
-
-    if (!setDefaultHash()) {
-      // An anchor was already present, trigger a request.
-      requestCurrentHash();
-    }
+    // Set the default hash.
+    window.location.hash = defaultHash;
   }
 
-  /// If no anchor is set, set the default anchor and return true.
-  /// Return false otherwise.
-  bool setDefaultHash() {
-    currentHash = window.location.hash;
-    if (currentHash == '' || currentHash == '#') {
-      window.location.hash = defaultHash;
-      return true;
-    }
-    return false;
+  /// Clear the current hash.
+  void clearCurrentHash() {
+    window.location.hash = '';
   }
 
   /// Refresh the service object reference in the location entry.
   void requestCurrentHash() {
     currentHash = window.location.hash;
-    assert(currentHash.startsWith('#/'));
-
+    if (!currentHash.startsWith('#/')) {
+      return;
+    }
     var parts = currentHash.substring(2).split('#');
     var location = parts[0];
     var args = (parts.length > 1 ? parts[1] : '');
     if (parts.length > 2) {
       Logger.root.warning('Found more than 2 #-characters in $currentHash');
     }
     _app.vm.get(currentHash.substring(2)).then((obj) {
         _app.response = obj;
         _app.args = args;
       });
   }
 }