1. The player doesn't acknowledge phantom stops when an exception is thrown anymore.
2. It also makes sure it doesn't reset the pendingPrepareCount unless it's actually
immediately acknowledging these prepares.
3. It ensures a seek is acknowledged even though an exception is thrown during seeking.
Added tests (which previously failed) for all three cases.
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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=178876362
318618d7a2