Disable the failing ThreadHelpers.* tests under ThreadSanitizer for now.

BUG=342305
TBR=jln@chromium.org

Review URL: https://codereview.chromium.org/158703002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@250062 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 250062