Really, given that the primary consumer of this API would be Electron and that it would take a huge coordination between OS and browser vendors to create a standard, it seems like it would be possible for Electron to just circumvent it and come up with their own way of sharing Chromiums between their own apps. When building you could specify whether you want your build to be fully portable, portable with the option of sharing, or fully reliant on a system-wide Chromium copy. On startup, an Electron app could check for an existing shared copy and automatically install its dependencies. The same could be done for Node.
It seems like that's not really going to work for the developers of these apps due to browser variation and version skew? (If it were okay, why aren't they supporting web browsers already?) But maybe apps on the same version of Electron could share a runtime?
Discord, to take an example, does support running in a browser. It's how I usually run it.
It also comes as an Electron app, because it wants more system privileges than browser tabs are ever allowed to get -- to tell people what game you're playing.
Web developers are already accustomed to supporting much more widely-varying browser versions, and web standards are expressly designed to be backwards-compatible basically forever. I don't think it would be a major problem.
