Remove heap snapshot size limit.

Remove heap snapshot size limit.

As long as frontend now stores snapshots in external arrays
it doesn't make sense to check the collected snapshot size on the
backend side. In other words if backend has managed to fit the
collected snapshot into its memory, it should also fit into the
frontend's memory.

R=yurys@chromium.org
BUG=chromium:232305

Review URL: https://codereview.chromium.org/14246029

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@14356 ce2b1a6d-e550-0410-aec6-3dcde31c8c00