For applications with a strict filesize limit for debug files, I added an option to specify a maximum filesize for AEC dumps. An existing unit test is extended to check that the feature works as advertised. BUG=webrtc:4741 TBR=glaznev@webrtc.org Review URL: https://codereview.webrtc.org/1413483003 Cr-Commit-Position: refs/heads/master@{#11081}