When we're going to parse multiple scripts in parallel, we cannot have the
Isolate count the ast node ids.

Now the counter is stored in CompilationInfo instead. This is because we need to
add ast nodes after parsing too.

R=rossberg@chromium.org
BUG=

Review URL: https://codereview.chromium.org/490173002

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@23301 ce2b1a6d-e550-0410-aec6-3dcde31c8c00