[webkit-dev] Pixel output for text/plain responses in layout tests

[Mihai Parparita]

I've been working on updating pixel baselines for Snow Leopard, and
ran into a test that fails due to missing pixel baselines
(http/tests/incremental/slow-utf8-text.pl) and was surprised how we
ever passed this test.

As it turns out, this test just outputs a text/plain response, which
is special-cased by the various DRT implementations to simulate
LayoutTestController.dumpAsText being called. However, for the
Chromium port (which are the only ones to actually enable pixel tests
as far as I know), a text/plain content type turns off pixel output in
addition to turning on text output:

http://trac.webkit.org/browser/trunk/WebKitTools/DumpRenderTree/chromium/TestShell.cpp#L435

While for other ports, it just enables text output, but leaves pixel
output alone (i.e. enabled if -p was passed to run-webkit-tests):

http://trac.webkit.org/browser/trunk/WebKitTools/DumpRenderTree/mac/DumpRenderTree.mm#L916
http://trac.webkit.org/browser/trunk/WebKitTools/DumpRenderTree/gtk/DumpRenderTree.cpp#L505
http://trac.webkit.org/browser/trunk/WebKitTools/DumpRenderTree/win/DumpRenderTree.cpp#L675

I have a slight preference for the Chromium behavior (pixel baselines
are brittle/annoying to maintain, if the output is text then layout is
not relevant/interesting), but either way consistency between ports is
best. Does anyone have any opinions about this?

Mihai