DevTools: Calculate user object distances from Window not from NativeContext.

LayoutTests/inspector/profiler/heap-snapshot-test.js

 var initialize_HeapSnapshotTest = function() {
 
 InspectorTest.createHeapSnapshotMockFactories = function() {
 
 InspectorTest.createJSHeapSnapshotMockObject = function()
 {
     return {
         _rootNodeIndex: 0,
         _nodeTypeOffset: 0,
         _nodeNameOffset: 1,
@@ skipping 168 matching lines @@
 
 InspectorTest.HeapNode.Type = {
     "hidden": "hidden",
     "array": "array",
     "string": "string",
     "object": "object",
     "code": "code",
     "closure": "closure",
     "regexp": "regexp",
     "number": "number",
-    "native": "native"
+    "native": "native",
+    "synthetic": "synthetic"
 };
 
 InspectorTest.HeapNode.prototype = {
     linkNode: function(node, type, nameOrIndex)
     {
         if (!this._builder)
             throw new Error("parent node is not connected to a snapshot");
 
         if (!node._builder)
             node._setBuilder(this._builder);
@@ skipping 177 matching lines @@
 
     var seed = 881669;
     function pseudoRandom(limit) {
         seed = ((seed * 355109 + 153763) >> 2) & 0xffff;
         return seed % limit;
     }
 
     var builder = new InspectorTest.HeapSnapshotBuilder();
     var rootNode = builder.rootNode;
 
-    var gcRootsNode = new InspectorTest.HeapNode("(GC roots)");
+    var gcRootsNode = new InspectorTest.HeapNode("(GC roots)", 0, InspectorTest.HeapNode.Type.synthetic);
     rootNode.linkNode(gcRootsNode, InspectorTest.HeapEdge.Type.element);
 
     var windowNode = new InspectorTest.HeapNode("Window", 20);
     rootNode.linkNode(windowNode, InspectorTest.HeapEdge.Type.shortcut);
     gcRootsNode.linkNode(windowNode, InspectorTest.HeapEdge.Type.element);
 
     for (var i = 0; i < instanceCount; ++i) {
         var sizeOfB = pseudoRandom(20) + 1;
         var nodeB = new InspectorTest.HeapNode("B", sizeOfB, undefined, firstId++);
         windowNode.linkNode(nodeB, InspectorTest.HeapEdge.Type.element);
@@ skipping 327 matching lines @@
         function sortingComplete()
         {
             dataGrid.removeEventListener(WebInspector.HeapSnapshotSortableDataGrid.Events.SortingComplete, sortingComplete, null);
             callback();
         }
         dataGrid.addEventListener(WebInspector.HeapSnapshotSortableDataGrid.Events.SortingComplete, sortingComplete, null);
     }
 };
 
 };