draft CL at https://chromium-review.googlesource.com/c/chromium/src/+/716852 .

You should put together a 1-pager on what you want to accomplish here and share it with chromium-dev@ for feedback.

yeah, i probably should.  i want to try it out in the d3d11 decoder or mcvd before i bother too many folks.  i might decide that i hate it in actual use.

sgtm, just keep in mind that since you're touching a bunch of base/ classes you'll need to involve folk sooner if you plan to commit your experiments :)

that's true.

i specifically backed off some of the base changes just to keep it smaller.  the new code closely mirrors existing code for scoped_refptr checking.

what i really wanted to do is let individual classes (that base has never heard of, like, oh, media/ :) ) provide custom base::Bind type checks via template specialization.  i couldn't figure out how to make templates that smart.  there seems to be a rule about needing to have the specialization defined before the template (base::Bind) that uses it is defined, rather than just instantiated.

if i could do that, then it's a very small change to base that makes type checking in base::Bind self-service.