[chromecast ]Add ChannelLayout to chromecast::media::AudioConfig

With ChannelLayout, IsValidConfig() can determine if the config
is valid without the workaround.

Bug: internal b/126765436
Merge-With: eureka-internal/249019
Test: mannually compile and cast.
Change-Id: Ib96054cb2e83cfdb03898d90d5ac823ca917e540
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1500015
Reviewed-by: Yuchen Liu <yucliu@chromium.org>
Reviewed-by: Kenneth MacKay <kmackay@chromium.org>
Commit-Queue: Guohui Deng <guohuideng@chromium.org>
Cr-Commit-Position: refs/heads/master@{#640997}
5 files changed