when running
$ gn gen out/Debug64

with run_findbugs = true and a webview_framework_jar the warning for the second argument gets masked by the first one.
i.e. the script reports only the first warning as below:

"
WARNING at build arg file (use "gn args <out_dir>" to edit):12:16: Build argument has no effect.
run_findbugs = true
               ^---
The variable "run_findbugs" was set as a build argument
but never appeared in a declare_args() block in any buildfile.
"