Redo LocationManager to use HTML5 History API

runtime/bin/vmservice/client/lib/service_html.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 service_html;
 
 import 'dart:async';
 import 'dart:convert';
 import 'dart:html';
 
@@ skipping 14 matching lines @@
       // that the Observatory is loaded from.
       host = 'http://${window.location.host}/';
     } else {
       // Otherwise, assume we are running from the Dart Editor and
       // want to connect on the default port.
       host = 'http://127.0.0.1:8181/';
     }
   }
 
   Future<String> getString(String id) {
+    // Ensure we don't request host//id.
+    if (host.endsWith('/') && id.startsWith('/')) {
+      id = id.substring(1);
+    }
     Logger.root.info('Fetching $id from $host');
-    return HttpRequest.getString(host + id).catchError((error) {
+    return HttpRequest.request(host + id,
+                               requestHeaders: {
+                                  'Observatory-Version': '1.0'
+                               }).then((HttpRequest request) {
+        return request.responseText;
+      }).catchError((error) {
       // If we get an error here, the network request has failed.
-      Logger.root.severe('HttpRequest.getString failed.');
+      Logger.root.severe('HttpRequest.request failed.');
       var request = error.target;
       return JSON.encode({
           'type': 'ServiceException',
           'id': '',
-          'response': error.target.responseText,
+          'response': request.responseText,
           'kind': 'NetworkException',
-          'message': 'Could not connect to service. Check that you started the'
-                     ' VM with the following flags:\n --enable-vm-service'
-                    ' --pause-isolates-on-exit'
+          'message': 'Could not connect to service (${request.statusText}). '
+                     'Check that you started the VM with the following flags: '
+                     '--observe'
         });
     });
   }
 }
 
 class WebSocketVM extends VM {
   final Map<int, Completer> _pendingRequests =
       new Map<int, Completer>();
   int _requestSerial = 0;
 
@@ skipping 96 matching lines @@
     message['id'] = idString;
     message['method'] = 'observatoryQuery';
     message['query'] = '/$path';
     _requestSerial++;
     var completer = new Completer();
     _pendingRequests[idString] = completer;
     window.parent.postMessage(JSON.encode(message), '*');
     return completer.future;
   }
 }