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This is part of the work of refactoring the iOS audio playback logic.

This CL implements the AudioPlaybackSink for iOS using the AudioQueue
API. The implementation is following Apple's guide for the playback
process:
https://developer.apple.com/library/archive/documentation/MusicAudio/Conceptual/AudioQueueProgrammingGuide/AboutAudioQueues/AboutAudioQueues.html#//apple_ref/doc/uid/TP40005343-CH5-SW22

In the next CL there will be an AudioPlaybackStream class that
connects the AudioJitterBuffer with AudioPlaybackSinkIos.

Bug: 868088
Change-Id: Ifbaa08bfcf5f983587bfb71418c681001ab7cdca
Reviewed-on: https://chromium-review.googlesource.com/1166246
Commit-Queue: Yuwei Huang <yuweih@chromium.org>
Reviewed-by: Joe Downing <joedow@chromium.org>
Cr-Commit-Position: refs/heads/master@{#581800}