Remove dependency of URLPattern class in NaCl code.

The debug stub is more a feature for the embedder
therefore the patch adds a public interface to
nacl_browser that Chrome implements.

This is part of an effort to componentize NaCl code.

BUG=244791

Review URL: https://codereview.chromium.org/32473003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@230121 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 230121