This merges the check if a protector is intact with the recording of
the dependency on it, at least in many cases.

Also introduce convenience functions to avoid the heap broker clutter.

Change-Id: I35508c4685a2f0df77819bf81075dd14a30e7e4f
Reviewed-on: https://chromium-review.googlesource.com/c/1487491
Commit-Queue: Georg Neis <neis@chromium.org>
Reviewed-by: Benedikt Meurer <bmeurer@chromium.org>
Reviewed-by: Jaroslav Sevcik <jarin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#59924}