[GTTF] Add an always-working timeout for browser_tests.

This one is implemented in the out-of-process launcher, so it's guaranteed
to work.

Not removing the MessageLoop delayed task sent inside the test because
currently not all browser tests use the launcher (sync tests?).

TEST=browser_tests
BUG=38053

Review URL: http://codereview.chromium.org/949002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@41694 0039d316-1c4b-4281-b951-d872f2087c98

• base/process_util.h[diff]
• base/process_util_posix.cc[diff]
• base/process_util_win.cc[diff]
• chrome/test/test_launcher/out_of_proc_test_runner.cc[diff]