Also removed Logger fields that used to be used for writing compressed logs.

BUG=None
R=bmeurer@chromium.org, loislo@chromium.org

Review URL: https://codereview.chromium.org/20768002

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@15941 ce2b1a6d-e550-0410-aec6-3dcde31c8c00