Bitrate controller for VideoToolbox encoder.

Also fixes a crash on encoder Release.

BUG=webrtc:4081

Review URL: https://codereview.webrtc.org/1660963002

Cr-Commit-Position: refs/heads/master@{#11729}
diff --git a/webrtc/modules/video_coding/video_coding.gypi b/webrtc/modules/video_coding/video_coding.gypi
index 438d8f1..94028a9 100644
--- a/webrtc/modules/video_coding/video_coding.gypi
+++ b/webrtc/modules/video_coding/video_coding.gypi
@@ -22,6 +22,7 @@
       ],
       'sources': [
         # interfaces
+        'include/bitrate_adjuster.h',
         'include/video_coding.h',
         'include/video_coding_defines.h',
 
@@ -54,6 +55,7 @@
         'video_coding_impl.h',
 
         # sources
+        'bitrate_adjuster.cc',
         'codec_database.cc',
         'codec_timer.cc',
         'content_metrics_processing.cc',