Once the SwarmingBucket work is done, we'd better look into this one.

Is there something that makes you think this is CrOS-specific? 

My guess is that this file depends on a bunch of generated targets (like mojo files) and that means you end up having to build a bunch of things. Copying a couple of other folks to confirm, though

also, IIUC these aren't necessarily clobber builds, but I'm guessing that whatever might exist on this bot before might be way out of date (judging by the very low build number) and so everything is being built from scratch in a way that might not happen on a much more commonly-used bot.

I guess I would start by trying to recreate those builds from scratch in a linux checkout, to figure out if this is something findit-specific, or cros-specific, or just the way it is if you want to build that particular file.

If it is cros-specific, or cros-builder-specific, I'd probably dig in to how the environment might be changing from build to build; maybe something is causing your command lines to change and force everything to be recompiled?

What exactly is a 'ninja edge'? Does it correspond to a gn target? A single file that needs some action (like a compile)? If it's 11,000 files that need to be compiled before payment_request_sheet_controller.cc that actually seems low. I'm pretty sure a from scratch build of chrome for chromeos is ~30k files. Code in c/b/ui sits at the top of the dependency stack, so I would expect payment_request_sheet_controller to require more than 11k to be built before it could be built.