GitLab

The motivation for this CL is because it is not very obvious on how to submit when tree is closed in git.

Also added a section 'How to submit when tree is closed' in https://sites.google.com/site/skiadocs/developer-documentation/tree-sheriff

(SkipBuildbotRuns)
Review URL: https://codereview.chromium.org/13932026

git-svn-id: http://skia.googlecode.com/svn/trunk@8666 2bbb7eff-a529-9590-31e7-b0007b416f81