Use correct format for size_t in child_process_logging_mac.mm
Use correct format for size_t in child_process_logging_mac.mm

This generates a warning on XCode 4.3.x.

BUG=108194
TEST=
TBR=thakis@chromium.org

Review URL: https://chromiumcodereview.appspot.com/9699111

git-svn-id: de016e52bd170d2d4f2344f9bf92d50478b649e0@127143 0039d316-1c4b-4281-b951-d872f2087c98

yitian134/chromium,gavinp/chromium,ropik/chromium,adobe/chromium,adobe/chromium,gavinp/chromium,gavinp/chromium,gavinp/chromium,yitian134/chromium,adobe/chromium,adobe/chromium,adobe/chromium,adobe/chromium,yitian134/chromium,ropik/chromium,gavinp/chromium,adobe/chromium,ropik/chromium,adobe/chromium,gavinp/chromium,ropik/chromium,adobe/chromium,ropik/chromium,ropik/chromium,yitian134/chromium,yitian134/chromium,yitian134/chromium,ropik/chromium,adobe/chromium,yitian134/chromium,gavinp/chromium,gavinp/chromium,yitian134/chromium,gavinp/chromium,gavinp/chromium,adobe/chromium,yitian134/chromium,ropik/chromium,ropik/chromium,yitian134/chromium