Remove metrics_default from rtc_media dependencies.

By not providing the default implementation of the metrics API
it becomes possible for users of rtc_media to choose which
implementation to use. The dependency is moved into each test
target that uses it instead.

NOTRY=True
NOPRESUBMIT=True

Review-Url: https://codereview.webrtc.org/2026223002
Cr-Original-Commit-Position: refs/heads/master@{#12991}
Cr-Mirrored-From: https://chromium.googlesource.com/external/webrtc
Cr-Mirrored-Commit: 98bba3981685bc61442a6e0f2bca70eb90d7837a
1 file changed