* JS_ERROR_TYPE is required for postmortem tools to inspect JSError
    objects (see https://github.com/nodejs/llnode/pull/215 for a usage
    example)
  * The context embedder index is required for postmortem tools to
    access embedder data stored in the context (see
    https://github.com/nodejs/llnode/pull/204 for a usage example)

R=bmeurer@google.com, yangguo@google.com

Change-Id: Ib7c7eb44f6ad327fc71a1d45f510c49377db7a25
Reviewed-on: https://chromium-review.googlesource.com/1138493Reviewed-by: Benedikt Meurer <bmeurer@chromium.org>
Commit-Queue: Benedikt Meurer <bmeurer@chromium.org>
Cr-Commit-Position: refs/heads/master@{#54475}