Similarly to how we check whether the entered context has access to the target
context when invoking the function constructor, we should check the involved
contexts before invoking eval().

I forgot to add this in the initial CL that adds the check for the function
constructor. Move the code to a common location, and use it for the GlobalEval
builtin as well.

BUG=chromium:541703
R=verwaest@chromium.org

Review-Url: https://codereview.chromium.org/2199343002
Cr-Commit-Position: refs/heads/master@{#38277}