Clean up V4L2 codec-related flags and defines

content/common/common.gni

 # Copyright 2014 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 # This file defines the content common gypi values. This file is read once and
 # cached, which is a performance optimization that allows us to share the
 # results of parsing the .gypi file between the public and private BUILD.gn
 # files. It also saves us from duplicating this exec_script call.
 content_common_gypi_values =
     exec_script("//build/gypi_to_gn.py",
                 [ rebase_path("../content_common.gypi") ],
                 "scope",
                 [ "../content_common.gypi" ])
 
 declare_args() {
-  # TODO(henryhsu): This flag should be removed after the linux header of
-  # trybot is updated.
-  # Indicates if Video4Linux2 codec is used. This is used for x86 CrOS
-  # platform which has v4l2 hardware encoder / decoder.
+  # Indicates if V4L plugin is used.
+  use_v4lplugin = false
+
+  # Indicates if Video4Linux2 codec is used. This is used for all CrOS
+  # platforms which have v4l2 hardware encoder / decoder.
   use_v4l2_codec = false
 }