Version 3.19.18.3.

Merged r15226 into trunk branch.

Merge assignment handling for Assignment and CompoundAssignment

R=verwaest@chromium.org

Review URL: https://codereview.chromium.org/16870013

git-svn-id: https://v8.googlecode.com/svn/trunk@15251 ce2b1a6d-e550-0410-aec6-3dcde31c8c00