Google says go Speed Tracer for Chrome
The timeline functionality was recently introduced as an enhancement to Chrome and Speed Tracer builds on that to display a "sluggishness graph" with time along the x-axis and Sluggishness (events) along the y-axis. The Apache 2.0 licensed project is documented on the GWT Speed Tracer page, complete with an tutorial video and example scenarios. Developers can find the source code on the project's Google Code page.
Speed Tracer is available on Windows and Linux versions of Google Chrome, where Google have enabled Chrome Extensions; currently, extensions are disabled on the beta version of Chrome for Mac OS X. Speed Tracer has been developed as part of the Google Web Toolkit (GWT) but is capable of analysing web performance for any web application.