This will allow us to move expressions from one function to another, for
example when the parser determines that a given cover grammar instance
is actually the default value initializer for an arrow function.

This is a re-land of https://codereview.chromium.org/636403003/ with a
fix for the arm64 code generator.

R=svenpanne@chromium.org
BUG=

Review URL: https://codereview.chromium.org/663373003

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@24769 ce2b1a6d-e550-0410-aec6-3dcde31c8c00