Clean up V4L2 codec-related flags and defines

content/common/common.gni

Index: content/common/common.gni
diff --git a/content/common/common.gni b/content/common/common.gni
index e192ae281c26b101357b54bd6f794e11e278c52d..597cd1b5e2369a454ae60b29be71e37dccdb9a07 100644
--- a/content/common/common.gni
+++ b/content/common/common.gni
@@ -13,9 +13,10 @@ content_common_gypi_values =
                 [ "../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
 }