Using a single bit in the inner function description preparse data of the
parent function we can avoid storing many NULL values for empty inner function
data.

This saves roughly 40KB out of 140KB PreparseScopeData on cnn.com.

Change-Id: Ib6019a8ceb99e772b398198074e171f635c0556e
Reviewed-on: https://chromium-review.googlesource.com/c/1405038
Commit-Queue: Camillo Bruni <cbruni@chromium.org>
Reviewed-by: Toon Verwaest <verwaest@chromium.org>
Cr-Commit-Position: refs/heads/master@{#58708}