Fix AudioPipeReader to use default pipe buffer size.
Pulseaudio uses default pipe buffer size to calculate pipe
latency, ignoring the actual buffer size set by the reading
side. AudioPipeReader was setting buffer size that's about 2
times bigger than default. As result it reports incorrect
latency and some clients did not work properly (particularly
AudioContext API implementation in chrome). Now
AudioPipeReader will be using default buffer size determined
by the OS, which matches pulseaudio's behavior.
BUG=442455
R=lambroslambrou@chromium.org
Review URL: https://codereview.chromium.org/
824943002
Cr-Commit-Position: refs/heads/master@{#309593}