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- Before changing the IO buffer size on the AudioUnit, see if the device still
  is present.
- Initialize min and max variables for buffer size range.
- Check return value when getting buffer size range; return at failure.

Bug: 960736
Change-Id: Iddf1d1736c801c46b690e6fe4a570b62f304830c
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1602493
Commit-Queue: Henrik Grunell <grunell@chromium.org>
Reviewed-by: Max Morin <maxmorin@chromium.org>
Reviewed-by: Oskar Sundbom <ossu@chromium.org>
Cr-Commit-Position: refs/heads/master@{#658550}