Add TimeDelta interfaces for WaitForExitCodeWithTimeout() functions.

Adding these interfaces will help update code that uses TestTimeouts::foo_timeout_ms()
to use TestTimeouts::foo_timeout() instead.  Old interfaces can get removed with
the TestTimeouts code.
R=jar@chromium.org
BUG=108171


Review URL: https://chromiumcodereview.appspot.com/10695117

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@145640 0039d316-1c4b-4281-b951-d872f2087c98

• base/process_util.h[diff]
• base/process_util_posix.cc[diff]
• base/process_util_win.cc[diff]