audio_processing/aec: Increased delay metrics aggregation window to five seconds
audio_processing/aec: Increased delay metrics aggregation window to five seconds

The known clients (GetStats and UMA histogram in Chrome) use at least 5 second aggregation window. There is no particular value in calculating the metrics more often.

The CL also includes a small refactoring moving a declaration inside an if statement.

BUG=2994
TEST=N/A
R=kwiberg@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/40219004

Cr-Original-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#8619}
Cr-Mirrored-From: https://chromium.googlesource.com/external/webrtc
Cr-Mirrored-Commit: d7a212e8b9c76b7c6eaefc6a432b2422b3fe0ab9

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