Fix many warnings/errors when building Observatory

runtime/observatory/lib/src/elements/cpu_profile/virtual_tree.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.
 
 import 'dart:async';
 import 'dart:html';
 import 'dart:math' as Math;
 import 'package:observatory/models.dart' as M;
 import 'package:observatory/src/elements/stack_trace_tree_config.dart'
     show ProfileTreeMode;
@@ skipping 31 matching lines @@
   Iterable<M.CallTreeNodeFilter> get filters => _filters;
 
   set direction(M.ProfileTreeDirection value) =>
       _direction = _r.checkAndReact(_direction, value);
   set mode(ProfileTreeMode value) => _mode = _r.checkAndReact(_mode, value);
   set filters(Iterable<M.CallTreeNodeFilter> value) {
     _filters = new List.unmodifiable(value);
     _r.dirty();
   }
 
-  factory CpuProfileVirtualTreeElement(
-      M.IsolateRef isolate, M.SampleProfile profile,
+  factory CpuProfileVirtualTreeElement(Object owner, M.SampleProfile profile,
       {ProfileTreeMode mode: ProfileTreeMode.function,
       M.SampleProfileType type: M.SampleProfileType.cpu,
       M.ProfileTreeDirection direction: M.ProfileTreeDirection.exclusive,
       RenderingQueue queue}) {
     assert(profile != null);
     assert(mode != null);
     assert(direction != null);
     CpuProfileVirtualTreeElement e = document.createElement(tag.name);
     e._r = new RenderingScheduler(e, queue: queue);
-    e._isolate = isolate;
+    e._isolate = owner;
     e._profile = profile;
     e._mode = mode;
     e._type = type;
     e._direction = direction;
     return e;
   }
 
   CpuProfileVirtualTreeElement.created() : super.created();
 
   @override
@@ skipping 36 matching lines @@
           tree = _profile.loadCodeTree(_direction);
         } else if (mode == ProfileTreeMode.function) {
           update = _updateMemoryFunctionRow;
           tree = _profile.loadFunctionTree(_direction);
         } else {
           throw new Exception('Unknown ProfileTreeMode: $mode');
         }
         break;
       default:
         throw new Exception('Unknown SampleProfileType: $type');
-        break;

[rmacnak, 2017/03/29 17:20:44]

I think the analyzer has gone back and forth on which it wants here.

     }
     if (filters != null) {
       tree = filters.fold(tree, (tree, filter) {
         return tree?.filtered(filter);
       });
     }
     if (tree == null) {
       children = [new HeadingElement.h1()..text = 'No Results'];
       return;
     }
@@ skipping 137 matching lines @@
   static _updateLines(List<Element> lines, int n) {
     n = Math.max(0, n);
     while (lines.length > n) {
       lines.removeLast();
     }
     while (lines.length < n) {
       lines.add(new SpanElement());
     }
   }
 }