[webkit-dev] Chromium "GPU" LayoutTests

[Adam Barth]

I've been trying to wrap my mind around the "GPU" LayoutTests that
Chromium runs.  In
<http://trac.webkit.org/browser/trunk/LayoutTests/platform>, there are
the following directories:

chromium-gpu
chromium-gpu-cg-mac
chromium-gpu-linux
chromium-gpu-win

These seem to be related to the webkit_gpu_tests step on these bots:

http://build.chromium.org/p/chromium.webkit/builders/Webkit%20Mac10.5%20%28CG%29
http://build.chromium.org/p/chromium.webkit/builders/Webkit%20Mac10.6%20%28CG%29
http://build.chromium.org/p/chromium.webkit/builders/Webkit%20Linux
http://build.chromium.org/p/chromium.webkit/builders/Webkit%20Vista
http://build.chromium.org/p/chromium.webkit/builders/Webkit%20Win7

This file <http://trac.webkit.org/browser/trunk/Tools/Scripts/webkitpy/layout_tests/port/builders.py>
also lists the following bots:

Webkit Win - GPU
Webkit Win7 - GPU
Webkit Linux - GPU
Webkit Linux 32 - GPU
Webkit Mac10.5 (CG) - GPU
Webkit Mac10.6 (CG) - GPU

Questions:

1) Do these "- GPU" bots exist anywhere?  (I can't find them, and a
recent bug comment indicates that they might be fictional.)
2) Are there any other bots related to the GPU configuration other
than those listed above?  (For example, is there any coverage of this
configuration on build.webkit.org?)
3) Why is webkit_gpu_tests a separate step from webkit_tests?

As far as I can tell, other ports, such as Apple-Mac, make use of the
GPU but don't impose as large a complexity tax on the project.  Is
there something different about Chromium's GPU support that requires
this additional complexity?

Adam