Fix clang warning about format string.
Fix clang warning about format string.

Patch by Nico Weber <thakis@chromium.org>.

Review URL: https://breakpad.appspot.com/348001/


git-svn-id: 7939527bf0a06ad24ad020f729d5600cb42ed5d7@914 4c0a9323-5329-0410-9bdc-e9ce6186880e

mikewied/breakpad,mikewied/breakpad,mikewied/breakpad,mikewied/breakpad,mikewied/breakpad,mikewied/breakpad