Calculate audio levels in AEC in time domain.
Calculate audio levels in AEC in time domain.

In AEC, audio levels are calculated in frequency domain. This makes the calculation dependent on FFT. We now make the calculation performed in time domain. The complexity is the same, but the dependence on FFT is removed.

BUG=

Review URL: https://codereview.webrtc.org/1542573002

Cr-Original-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#11357}
Cr-Mirrored-From: https://chromium.googlesource.com/external/webrtc
Cr-Mirrored-Commit: 9846845da6ee88bf16cb5fc62c6839ed7aafe04c

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