Speedtracer cannot load html trace files it created about speedtracer HOT 4 OPEN

I hit this bug as well. The breakage seems to have been a change in chrome 
(Port no longer contains a Tab but a Sender).

Here is a patch that fixes the bug

What do I do with the patch?

Hopefully the maintainer has applied it/will apply it and publish an updated 
speedtracer to the store. Otherwise you could download the code, apply the 
patch and build the extension yourself. (it is a bit trick as it does not build 
in the current GWT version I think.) 

Attached a pre-built .CRX executable of Speed Tracer's SVN trunk with the patch 
applied.
To install it, just drag the .CRX to the Chrome Extensions page, as described 
here: http://stackoverflow.com/a/11879334

See below for detailed info.
============

- It seems the patch *was* already applied to Speed Tracer trunk (on Feb 27, 
2013) so I did not have to do it myself;
- However nobody had pushed a new Speed Tracer release... the one in the Chrome 
Web Store is still version 0.27 and dates back to Oct 10, 2012;
- If you want to build your own .CRX, just follow the build steps described 
here: https://code.google.com/p/speedtracer/wiki/BuildingSpeedTracer
** NOTE 1: On Windows, instead of cygwin (yuck!) you can use any command-line 
SVN binaries; there are quite a few on the Internet;
** NOTE 2: Probably for all OSes: make sure that you use SVN 1.6.X client, or 
the build process will fail in the middle. Reason: your SVN client is somehow 
only used for boot-strapping; in the middle of the the build, another, 
auto-downloaded SVN client takes over, and that other SVN client is old 
(1.6.6). If yours is newer, the old one will complain that the working copy has 
a newer format;
** NOTE 3: By default, the build will fail complaining that 
"speedtracerheadless.crx was not produced"; IMO this is not really needed 
(right?), and despite the failure, the speedtracer.crx file will be created 
successfully in the meantime...