Pepper: Remove old-style InterfaceList AddPPB.

InterfaceList currently has two different AddPPB() methods, one of which is
deprecated. This patch removes that version, and I'll send another for
AddPPP().

This is part of some small InterfaceList cleanup I'm doing while adding support
for "dev channel" APIs.

I tested this by loading a page in flash.

BUG=
R=dmichael@chromium.org

Review URL: https://codereview.chromium.org/108533002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@239264 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 239264