The AudioProcessing class is used as an interface
to the functionality in the audio processing module.
Therefore, it should be a pure interface.
This CL ensures that is the case.

BUG=webrtc:6515

Review-Url: https://codereview.webrtc.org/2406193002
Cr-Original-Commit-Position: refs/heads/master@{#14608}
Cr-Mirrored-From: https://chromium.googlesource.com/external/webrtc
Cr-Mirrored-Commit: 73a28ee066d62c238e8c669ab781bdf289b720ee
6 files changed