mac: use errno instead of return value of pthread_setname_np
mac: use errno instead of return value of pthread_setname_np

It appears the return value is always -1 on error.

BUG=47058

Review URL: http://codereview.chromium.org/2824018

git-svn-id: http://src.chromium.org/svn/trunk/src@50373 4ff67af0-8c30-449e-8e8b-ad334ec8d88c

Former-commit-id: 996652fa0a22f602b0560e14a684b293e2df5926
meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser