Fix circular dependencies between optional, array_view, and rtc_base.

This splits things out of rtc_base and makes dependencies explicit.

Bug: webrtc:6828
Change-Id: Id521896c3c43595349021c857bec216e429a0c8d
Reviewed-on: https://webrtc-review.googlesource.com/32780
Reviewed-by: Karl Wiberg <kwiberg@webrtc.org>
Commit-Queue: Patrik Höglund <phoglund@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#21264}
diff --git a/audio/BUILD.gn b/audio/BUILD.gn
index ef132cc..65e3050 100644
--- a/audio/BUILD.gn
+++ b/audio/BUILD.gn
@@ -54,6 +54,7 @@
     "../modules/pacing:pacing",
     "../modules/remote_bitrate_estimator:remote_bitrate_estimator",
     "../modules/rtp_rtcp",
+    "../rtc_base:checks",
     "../rtc_base:rtc_base",
     "../rtc_base:rtc_base_approved",
     "../rtc_base:rtc_task_queue",
@@ -113,6 +114,7 @@
       "../rtc_base:rtc_base_approved",
       "../rtc_base:rtc_base_tests_utils",
       "../rtc_base:rtc_task_queue",
+      "../rtc_base:safe_compare",
       "../system_wrappers:system_wrappers",
       "../test:audio_codec_mocks",
       "../test:rtp_test_utils",