Send uptime as milliseconds for Mac and iOS.

 All other platform are sending uptime as milliseconds. Changing the
implementation to do the same on Mac and iOS.
Review URL: https://breakpad.appspot.com/355001

git-svn-id: http://google-breakpad.googlecode.com/svn/trunk@928 4c0a9323-5329-0410-9bdc-e9ce6186880e
3 files changed