It looks to me like the stride is wrong when uploading from a PBO. CC'ing Olli though he won't be back for a couple of weeks.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/2a13149d256d49a1f569d884a6edcf8811c65a94

commit 2a13149d256d49a1f569d884a6edcf8811c65a94
Author: zmo <zmo@chromium.org>
Date: Mon May 23 22:16:58 2016

Set correct bug ID for a few webgl2 conformance test expectations.

BUG=614174, 614178 
TEST=no change
TBR=kbr@chromium.org
NOTRY=true
CQ_INCLUDE_TRYBOTS=tryserver.chromium.linux:linux_optional_gpu_tests_rel;tryserver.chromium.mac:mac_optional_gpu_tests_rel;tryserver.chromium.win:win_optional_gpu_tests_rel

Review-Url: https://codereview.chromium.org/2000313003
Cr-Commit-Position: refs/heads/master@{#395434}

[modify] https://crrev.com/2a13149d256d49a1f569d884a6edcf8811c65a94/content/test/gpu/gpu_tests/webgl2_conformance_expectations.py

Mac NVidia is not our target platform for initial WebGL2 release.  Make it non-blocking.

This issue has been Available for over a year. If it's no longer important or seems unlikely to be fixed, please consider closing it out. If it is important, please re-triage the issue.

Sorry for the inconvenience if the bug really should have been left as Available. If you change it back, also remove the "Hotlist-Recharge-Cold" label.

For more details visit https://www.chromium.org/issue-tracking/autotriage - Your friendly Sheriffbot