generate_build_files failing on chromium.linux/Android Arm64 Builder (dbg)

Type: build-failure

Information: The failure is on /b/c/b/Android_Arm64_Builder__dbg_/src/buildtools/linux64/gn gen //out/Debug --check
  -> returned 1
ERROR at build arg file (use "gn args <out_dir>" to edit):1:19: Build argument has no effect.
ffmpeg_branding = "Chrome"
                  ^-------
The variable "ffmpeg_branding" was set as a build argument
but never appeared in a declare_args() block in any buildfile.

Builders failed on: 
- Android Arm64 Builder (dbg): 
  https://build.chromium.org/p/chromium.linux/builders/Android%20Arm64%20Builder%20%28dbg%29