Make keyframe generation/request intervals configurable through field trials.

Bug: webrtc:10427
Change-Id: I5e7182fc8932943adc3e5f147be51b0b5df93172
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/127882
Reviewed-by: Åsa Persson <asapersson@webrtc.org>
Reviewed-by: Karl Wiberg <kwiberg@webrtc.org>
Reviewed-by: Jonas Oreland <jonaso@webrtc.org>
Reviewed-by: Philip Eliasson <philipel@webrtc.org>
Commit-Queue: Rasmus Brandt <brandtr@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#27233}
diff --git a/video/BUILD.gn b/video/BUILD.gn
index 0e02401..8f89e22 100644
--- a/video/BUILD.gn
+++ b/video/BUILD.gn
@@ -99,6 +99,7 @@
     "../rtc_base:stringutils",
     "../rtc_base:weak_ptr",
     "../rtc_base/experiments:alr_experiment",
+    "../rtc_base/experiments:keyframe_interval_settings_experiment",
     "../rtc_base/experiments:quality_scaling_experiment",
     "../rtc_base/experiments:rate_control_settings",
     "../rtc_base/system:fallthrough",