[Mac] Fix clang breakage in process_singleton_mac.cc.
[Mac] Fix clang breakage in process_singleton_mac.cc.

Not using the return value from close() is verboten.  Use the return
value.

Additionally, a late addition to the original CL asked for
clarification that kMaxErrno wasn't "too big".  Make it so.

BUG=none
TEST=clang builds.  histograms don't take up megabytes.

Review URL: http://codereview.chromium.org/3760005

git-svn-id: dd90618784b6a4b323ea0c23a071cb1c9e6f2ac7@62681 4ff67af0-8c30-449e-8e8b-ad334ec8d88c

wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser