During finalization, we create SharedFunctionInfos which in turn
will create ScopeInfos for the Scopes in the AST. The Scopes then
cache a handle to the ScopeInfos. However, once the scope is closed,
all those handles get zapped, and it's no longer possible to access
the scopes (even though we actually still need the AST).

R=rmcilroy@chromium.org
BUG=

Review-Url: https://codereview.chromium.org/2278933002
Cr-Commit-Position: refs/heads/master@{#38898}