Merged r19443 into trunk branch.

Add merge-to-branch python port.

R=jkummerow@chromium.org
BUG=

Review URL: https://codereview.chromium.org/167463005

git-svn-id: https://v8.googlecode.com/svn/trunk@19451 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
Merge remote-tracking branch 'upstream/trunk' into trunk