Merged r13380, r13381 into trunk branch.

Add sanity check to CodeFlusher::AddCandidate.

Fix windows build wrt symbol export.

BUG=chromium:169209

R=mstarzinger@chromium.org

Review URL: https://chromiumcodereview.appspot.com/11889031

git-svn-id: https://v8.googlecode.com/svn/trunk@13384 ce2b1a6d-e550-0410-aec6-3dcde31c8c00