Remove instrumentation for FileStream::Context::Close check failure.

The associated bugs have since been fixed.
This change is essentially a revert of cf470d52d8a5260a38accdc5335c86fa9afff879, but with some edits:

Instead of reverting to CHECK(!async_in_progress_) it restores to an earlier DCHECK(!async_in_progress_).

Bug: 487732, 656692
Change-Id: Ibde40e63a747bddd180ed680ebd63e0f8c729e97
Reviewed-on: https://chromium-review.googlesource.com/986647
Reviewed-by: Helen Li <[email protected]>
Commit-Queue: Eric Roman <[email protected]>
Cr-Commit-Position: refs/heads/master@{#546969}
4 files changed