Fix assertions wrt concurrent OSR.

R=ulan@chromium.org

Review URL: https://codereview.chromium.org/206473002

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@20130 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
A64: Restore the stack limit protection to 1KB.

R=ulan@chromium.org

Review URL: https://codereview.chromium.org/206393002

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@20131 ce2b1a6d-e550-0410-aec6-3dcde31c8c00