Add gfx_unittests as a valid option to tools/valgrind/chrome_tests.py.
Add gfx_unittests as a valid option to tools/valgrind/chrome_tests.py.

BUG=none
TEST=./tools/valgrind/chrome_tests.py -t gfx

Review URL: http://codereview.chromium.org/3959004

git-svn-id: dd90618784b6a4b323ea0c23a071cb1c9e6f2ac7@63563 4ff67af0-8c30-449e-8e8b-ad334ec8d88c

wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser