WebGLConformance: schedule per build in one suite.

I mistakenly assumed duplication removal worked across suites.
This change adds a graphics_per-build suite and uses it.

BUG=None.
TEST=None.

Change-Id: Id2799f6ad3393763d5389ea6bcfd99193c8c1cea
Reviewed-on: https://gerrit.chromium.org/gerrit/46659
Reviewed-by: Scott Zawalski <scottz@chromium.org>
Commit-Queue: Ilja H. Friedel <ihf@chromium.org>
Reviewed-by: Ilja H. Friedel <ihf@chromium.org>
Tested-by: Ilja H. Friedel <ihf@chromium.org>
4 files changed