Compilation failures are already stored in the {CompilationState}. We
never use the information which individual compilation unit failed.
Hence remove that getter, and only check for failure of the overall
compilation.

R=ahaas@chromium.org

Bug: v8:7921, v8:8343
Change-Id: Ibf90be233c9ff576ec8a3413ba5abefe2fdb645e
Reviewed-on: https://chromium-review.googlesource.com/c/1373783Reviewed-by: Andreas Haas <ahaas@chromium.org>
Commit-Queue: Clemens Hammacher <clemensh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#58195}