Revert "Make ReliableSurface's fallback buffer match ANW size"

This reverts commit 77477858.

Reason for revert: <Droid monitor: Likely culprit for b/403616834 - verifying through ABTD before revert submission. This is part of the standard investigation process, and does not mean your CL will be reverted.>

Change-Id: I495eae72dc0054bc6fff664c504e1305c269ce3f