SST - Web Test Framework: http://testutils.org/sst
The latest release of SST (0.2.0) adds the ability to capture HAR (HTTP Archive format) output for pageload performance tracing/profiling.
New SST doc section: Performance tracing with Browsermob Proxy (HAR)
The HAR format is based on JSON, and is used by tools that consume/produce data collected by monitoring HTTP communication. These files contain a log of HTTP client/server conversation and can be used for additional analysis of page load performance.
The capture is achieved by routing browser requests through BrowserMob Proxy, which records web page loads while your tests run. SST will launch the proxy and save output to .har files if you enable the `--browsermob` command line option. HAR files are saved in the results directory for each page load.
HAR files can be viewed/analyzed with various tools, such as `harviewer`:
I created a screencast demo showing it all together: