Deal with Javascript integer limitations in heap snapshot processing to handle 64-bit target VMs.

runtime/observatory/lib/src/elements/heap_snapshot.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 heap_snapshot_element;
 
 import 'dart:async';
 import 'dart:html';
 import 'observatory_element.dart';
 import 'package:observatory/app.dart';
@@ skipping 57 matching lines @@
     percentNode.title = "Percent of heap being retained";
     percentNode.style.display = 'inline-block';
     firstColumn.children.add(percentNode);
 
     var gap = new SpanElement();
     gap.style.minWidth = '1em';
     gap.style.display = 'inline-block';
     firstColumn.children.add(gap);
 
     AnyServiceRefElement objectRef = new Element.tag("any-service-ref");
-    String hexAddress = vertex.address.toRadixString(16);
-    snapshot.isolate.getObjectByAddress(hexAddress).then((obj) {
+    snapshot.isolate.getObjectByAddress(vertex.address).then((obj) {
       objectRef.ref = obj;
     });
     objectRef.style.alignSelf = 'center';
     firstColumn.children.add(objectRef);
 
     var secondColumn = flexColumns[1];
     secondColumn.style.justifyContent = 'flex-end';
     secondColumn.style.position = 'relative';
     secondColumn.style.alignItems = 'center';
     secondColumn.style.paddingRight = '0.5em';
@@ skipping 362 matching lines @@
 
     new Future.delayed(const Duration(milliseconds: 500), () {
       buildMergedVertices(snapshot.graph).then((vertices) {
         state = 'Loaded';
         var rootRow = new MergedVerticesRow(tree, null, isolate, vertices);
         tree.initialize(rootRow);
       });
     });
   }
 }