Grow heap slower if GC freed many global handles.

BUG=263503
LOG=Y
R=hpayer@chromium.org

Review URL: https://codereview.chromium.org/352763002

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@22003 ce2b1a6d-e550-0410-aec6-3dcde31c8c00