This is inital work in order to utilize CompilerDispatcher in parallel
parsing.

BUG=v8:6093

Change-Id: I6aae4f32ddb2314585d09039c1c5d7e658dc896f
Reviewed-on: https://chromium-review.googlesource.com/469709Reviewed-by: Marja Hölttä <marja@chromium.org>
Reviewed-by: Jochen Eisinger <jochen@chromium.org>
Commit-Queue: Wiktor Garbacz <wiktorg@google.com>
Cr-Commit-Position: refs/heads/master@{#44509}