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/modules/remote_bitrate_estimator/BUILD.gn b/modules/remote_bitrate_estimator/BUILD.gn
index 7c32ce1..93b8322 100644
--- a/modules/remote_bitrate_estimator/BUILD.gn
+++ b/modules/remote_bitrate_estimator/BUILD.gn
@@ -49,6 +49,7 @@
     "../../api:optional",
     "../../modules:module_api",
     "../../modules/rtp_rtcp:rtp_rtcp_format",
+    "../../rtc_base:checks",
     "../../rtc_base:rtc_base_approved",
     "../../system_wrappers",
     "../../system_wrappers:field_trial_api",
@@ -140,6 +141,7 @@
       "..:module_api",
       "../..:webrtc_common",
       "../../api:optional",
+      "../../rtc_base:checks",
       "../../rtc_base:gtest_prod",
       "../../rtc_base:rtc_base",
       "../../rtc_base:rtc_base_approved",
@@ -204,6 +206,7 @@
       ":bwe_simulator_lib",
       ":remote_bitrate_estimator",
       "../..:webrtc_common",
+      "../../rtc_base:checks",
       "../../rtc_base:rtc_base",
       "../../rtc_base:rtc_base_approved",
       "../../system_wrappers",