Add ability to save and load timelines from Observatory

runtime/observatory/lib/src/elements/timeline_page.dart

 // Copyright (c) 2015, 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 timeline_page_element;
 
 import 'dart:async';
 import 'dart:convert';
 import 'dart:html';
 import 'observatory_element.dart';
@@ skipping 49 matching lines @@
       'recordedStreams': ['all'],
     });
   }
 
   Future recordOff() async {
     return app.vm.invokeRpc('_setVMTimelineFlags', {
       'recordedStreams': [],
     });
   }
 
+  Future saveTimeline() async {
+    return postMessage('save');
+  }
+
+  Future loadTimeline() async {
+    return postMessage('load');
+  }
+
   _updateSize() {
     IFrameElement e = $['root'];
     final totalHeight = window.innerHeight;
     final top = e.offset.top;
     final bottomMargin = 32;
     final mainHeight = totalHeight - top - bottomMargin;
     e.style.setProperty('height', '${mainHeight}px');
     e.style.setProperty('width', '100%');
   }
 
 
   StreamSubscription _resizeSubscription;
 }