This is a minor follow up CL to our previous CL [1], which migrated
IME to handle back with OnBackInvokedDispatcher.
Having SomeArgs within SomeArgs doesn't make sense unless we really
run out of arguments.
This CL also addresses minor style issues.
Basically this is a mechanical clean-up that has no behavior change.
[1]: Ie207b63b11a56c9b2173f26b734a27b13ebccc60
a6666f2221
Bug: 228358882
Bug: 234882948
Test: presubmit
Change-Id: Ie14f66be0c9d66d221c5f9fae244df5487d65593
3a10176c60