Fix two bugs:
- Initial configuration of limit allowed to go below the size of already
  allocated objects.
- Context disposal without dependend context reset the heap state to not
  configured without actually increasing the limit again.

Bug: chromium:843903
Change-Id: Ibdcf69b0b92b800f8919d5cc98186334945d811f
Reviewed-on: https://chromium-review.googlesource.com/c/1355143Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Commit-Queue: Michael Lippautz <mlippautz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#57946}