Allow typing label names on Windows by not treating things that start with slashes as arguments rather than switches.

The old command line parsing is still run so some code could get confused later since / will also be treated as a switch if you ask for it. This seems not as likely to happen that the label will match a switch. If it does, we'll have to change the CommandLine class to make the "/" behavior optional.

Fix a "desc" crash attributing blame due to a null pointer.

BUG=
R=scottmg@chromium.org, thakis@chromium.org

Review URL: https://codereview.chromium.org/24613003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@225277 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 225277