> QCMS changes are currently triggering layouttests using a super hacky whitespace.txt change.

QCMS once used CQ_INCLUDE_TRYBOTS but that stopped working per [1], and the whitespace file that was used to convince the blink trys bots to run the layout tests was added back.

> Can you please add QCMS to the CHROMIUM_BLINK_TESTS_PATHS [1] list and remove LayoutTests/whitespace.txt?

Maybe, but why remove the whitespace.txt?  The issue is not specific to QCMS best I can tell - many third_party libraries can change Blink rendering, but I don't see any in chromium_trybot.py.

Perhaps there is some other way to force layout tests (dunno), but it seems the whitespace.txt file is all third_party libs have right now.

[1] https://codereview.chromium.org/1485583002#msg5

> Maybe, but why remove the whitespace.txt?

We should remove whitespace.txt because it is undocumented and brittle. If you forget to update whitespace.txt, the patch will land but a different commit will be blamed for the failures.

> The issue is not specific to QCMS best I can tell - many third_party libraries can change Blink rendering, but I don't see any in chromium_trybot.py.

Other libraries don't seem to be using LayoutTests/whitespace.txt. You hint that maybe there's a better approach to fixing this... can you investigate?

> We should remove whitespace.txt because it is undocumented and brittle. If you forget to update whitespace.txt, the patch will land but a different commit will be blamed for the failures.

This was the method we were given by infra (might make sense to talk to infra folks about it).

> Other libraries don't seem to be using LayoutTests/whitespace.txt.

Pretty sure third_party/libpng needed it recently.

> You hint that maybe there's a better approach to fixing this... can you investigate?

Adding third_party/* to chromium_trybot.py would maybe work better?  But again, that's really a question infra folks should answer.

> Pretty sure third_party/libpng needed it recently.

We could also expand the list of third_party projects that would affect Blink image rendering on updates to that project ...

third_party/libpng
third_party/libjpeg
third_party/libjpeg_turbo
third_party/libwebp
third_party/iccjpeg
third_party/qcms
third_party/zlib
third_party/yasm

+matt, leon: is the list given in #4 complete?  Did I miss anything?

You did not miss anything that I am aware of.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/tools/build.git/+/461efe12197b0745e8845a6a65a6e5af27d1abfc

commit 461efe12197b0745e8845a6a65a6e5af27d1abfc
Author: noel@chromium.org <noel@chromium.org>
Date: Thu Apr 07 11:13:17 2016

Run layout tests on image affecting third_party changes

BUG= 597181 

Review URL: https://codereview.chromium.org/1863333003

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/build@299760 0039d316-1c4b-4281-b951-d872f2087c98

[modify] https://crrev.com/461efe12197b0745e8845a6a65a6e5af27d1abfc/scripts/slave/recipes/chromium_trybot.py