Logger: reorder methods in log.cc

No logic changes.

BUG=none
TEST=current test set
TBR=yurys@chromium.org

Review URL: https://codereview.chromium.org/19724004

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@15785 ce2b1a6d-e550-0410-aec6-3dcde31c8c00