Only check errno when it can be set.
Only check errno when it can be set.

This is a follow-up after http://codereview.chromium.org/77022

Review URL: http://codereview.chromium.org/99055

git-svn-id: dd90618784b6a4b323ea0c23a071cb1c9e6f2ac7@14602 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