Lint clean video/ and add lint presubmit check.

BUG=webrtc:5316

Review URL: https://codereview.webrtc.org/1507643004

Cr-Commit-Position: refs/heads/master@{#10953}
diff --git a/PRESUBMIT.py b/PRESUBMIT.py
index d7c5ea2..be26269 100755
--- a/PRESUBMIT.py
+++ b/PRESUBMIT.py
@@ -19,6 +19,7 @@
   'webrtc/audio',
   'webrtc/call',
   'webrtc/modules/video_processing',
+  'webrtc/video',
 ]
 
 # List of directories of "supported" native APIs. That means changes to headers