Fixed Observatory class-view crash

runtime/observatory/lib/src/elements/class_view.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.
 
 library class_view_element;
 
 import 'dart:async';
 import 'observatory_element.dart';
 import 'sample_buffer_control.dart';
 import 'stack_trace_tree_config.dart';
@@ skipping 75 matching lines @@
     var progress = (await stream.first).progress;
     shadowRoot.querySelector('#sampleBufferControl')..children = [
       new SampleBufferControlElement(progress, stream, queue: app.queue,
           selectedTag: _tag)
         ..onTagChange.listen((e) {
           _tag = e.element.selectedTag;
           refreshAllocationProfile();
         })
     ];
     if (M.isSampleProcessRunning(progress.status)) {
-      progress = await stream.last;
+      progress = (await stream.last).progress;
     }
     if (progress.status == M.SampleProfileLoadingStatus.loaded) {
       shadowRoot.querySelector('#stackTraceTreeConfig')..children = [
         new StackTraceTreeConfigElement(
           queue: app.queue)
           ..showFilter = false
           ..onModeChange.listen((e) {
             cpuProfileTreeElement.mode = e.element.mode;
           })
           ..onDirectionChange.listen((e) {
@@ skipping 10 matching lines @@
   Future toggleAllocationTrace() {
     if (cls == null) {
       return new Future(refresh);
     }
     if (cls.traceAllocations) {
       refreshAllocationProfile();
     }
     return cls.setTraceAllocations(!cls.traceAllocations).whenComplete(refresh);
   }
 }