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

git-svn-id: http://src.chromium.org/chrome/trunk/src/testing@291176 4ff67af0-8c30-449e-8e8b-ad334ec8d88c