Heap stats is a HTML-based tool for visualizing V8-internal object statistics. For example, the tool can be used to visualize how much heap memory is used for maintaining internal state versus actually allocated by the user.
The tool consumes log files produced by d8 (or Chromium) by passing --trace-gc-object-stats or a trace captured using Chrome's tracing infrastructure. Chrome trace files need to be unpacked before they can be used though.
Hosting requires a web server, e.g.:
cd tools/heap-stats python -m SimpleHTTPServer 8000