Enable cpplint for webrtc/modules/bitrate_controller and fix all uncovered cpplint errors.

This CL enableds cpplint for webrtc/modules/bitrate_controller.

BUG=webrtc:5311
NOTRY=true

TESTED=Fixed issues reported by:
find webrtc/modules/bitrate_controller -type f -name *.cc -o -name *.h | xargs cpplint.py
followed by 'git cl presubmit'.

Review URL: https://codereview.webrtc.org/1620003003

Cr-Commit-Position: refs/heads/master@{#11363}
diff --git a/PRESUBMIT.py b/PRESUBMIT.py
index 08dd68d..3fb3ed1 100755
--- a/PRESUBMIT.py
+++ b/PRESUBMIT.py
@@ -20,6 +20,7 @@
   'webrtc/call',
   'webrtc/common_video',
   'webrtc/examples',
+  'webrtc/modules/bitrate_controller',
   'webrtc/modules/remote_bitrate_estimator',
   'webrtc/modules/rtp_rtcp',
   'webrtc/modules/video_coding',