systrace: add a tracing tag for video

Change-Id: I29d6d1fbf84668d003941e0d79fedb7d9e9c0ea2
diff --git a/systrace.py b/systrace.py
index dd53a61..98a143f 100755
--- a/systrace.py
+++ b/systrace.py
@@ -22,6 +22,7 @@
   'am':       1<<6,
   'sync':     1<<7,
   'audio':    1<<8,
+  'video':    1<<9,
 }
 
 def main():