Changes from WebPagetest 2.12:

First, a big thank you to the community, there were several patches from external contributors in this release.

Web Server

Integration with Appurify for mobile testing as a service (including traffic shaping, native browsers, full timeline capture and high-framerate video).
Integration with TSViewDB for time-series data storage and reporting.
Added a multi-waterfall view to the filmstrip comparisons to present overlaid waterfalls.
Added a main-thread breakdown view for Chrome timelines to show where the browser spent it's time.
Added an "Effective Bps" metric that calculates the bandwidth used from the first byte to the end of the load to show how efficiently a site is filling the pipe.
Fixed the EC2 auto-scaling logic to account for pending spot instance requests.
Added support for overriding the default connectivity on a per-location basis.
Added a link to the request details popup to open the response body in a new window (if bodies were captured).
Significantly improved the error messaging when tests fail (will now indicate why it failed to run the test).

Significant fixes to IE testing (some of those "how did it ever work" kind of fixes).
Updates to support newer Chrome and Firefox releases.
Added support for arbitrary command-line options for Chrome.
Improvements to the emulated mobile testing.

Removed support for automatically rebooting.
Significantly simplified the agent code and stripped out all of the legacy non-WebPagetest code.
Fixes to make agent more stable (keep running without intervention).

Added reporting of msFirstPaint from window.performance (IE only).
Added a CPU Time metric to report how much CPU-busy time was consumed while loading the page.
Added reporting of agent CPU utilization (for tracking down under-provisioned agents).
Improved IE's cache clearing to be more reliable.