Add missing test targets to the Linux ASan bots on chromium.memory.

Add missing test targets to the Linux ASan bots on chromium.memory.

When converting those bots to recipes in r287833, "unit" was replaced with
"unit_tests". In fact, "unit" is a composite step that includes 5 other targets
besides "unit_tests". This CL adds those targets back.

This CL also adds accessibility_unittests and gfx_unittests, which presently run
on the linux_asan trybot and on other waterfalls, but not on chromium.memory.
The same should be done to cast_unittests and google_apis_unittests, once they
are green under ASan.

BUG=none
R=glider@chromium.org
TBR=phajdan.jr@chromium.org
NOTRY=true

Review URL: https://codereview.chromium.org/498443002

Cr-Commit-Position: refs/heads/master@{#291176}
git-svn-id: svn://svn.chromium.org/chrome/trunk/src@291176 0039d316-1c4b-4281-b951-d872f2087c98