DevTools: Speed up timeline aggregated tree building.

third_party/WebKit/LayoutTests/http/tests/inspector/timeline-test.js

Index: third_party/WebKit/LayoutTests/http/tests/inspector/timeline-test.js
diff --git a/third_party/WebKit/LayoutTests/http/tests/inspector/timeline-test.js b/third_party/WebKit/LayoutTests/http/tests/inspector/timeline-test.js
index cc63fedc203e39ed3bbbc6b28a0a5fbf42674118..e2ab4794e875cef26f7c24bb16336c85eb5ee178 100644
--- a/third_party/WebKit/LayoutTests/http/tests/inspector/timeline-test.js
+++ b/third_party/WebKit/LayoutTests/http/tests/inspector/timeline-test.js
@@ -226,8 +226,7 @@ InspectorTest.walkTimelineEventTreeUnderNode = function(callback, root, level)
     var event = root.event;
     if (event)
         callback(event, level)
-    var children = root.children ? root.children.values() : [];
-    for (var child of children)
+    for (var child of root.children().values())
         InspectorTest.walkTimelineEventTreeUnderNode(callback, child, (level || 0) + 1);
 }