Unpack different wav files after each INIT event of the aecdump

Some aecdumps have more than one INIT event. In those cases only the last wav file was unpacked, which sometimes is not the most interesting or desired one.
This CL creates a different wav file after each INIT event.

Review-Url: https://codereview.webrtc.org/2067423002
Cr-Original-Commit-Position: refs/heads/master@{#13196}
Cr-Mirrored-From: https://chromium.googlesource.com/external/webrtc
Cr-Mirrored-Commit: f03a8d4c4dabcc18b36bce6b093b7a8c29eca379
1 file changed