Add extra overrides to BrowserTestPortOverrides to remove extra switches for running browser_tests.

check_sys_deps() is overridden to return None since checking for system dependencies isn't necessary.

driver_name() is overridden to return browser_tests because browser_tests is the only driver that should be run on the BrowserTest platform.

default_timeout_ms() is overridden because there needs to a longer timeout, especially on Windows.

BUG=388517

Review URL: https://codereview.chromium.org/434513003

git-svn-id: svn://svn.chromium.org/blink/trunk@179751 bbb929c8-8fbe-4397-9dbb-9b2b20218538