New SchemeRegistry list for schemes with predefined custom handlers

[Javier Fernandez]

Hi content-owners,

I'm reaching out here with the hope my proposal will be relevant for the
right people. If it's not the case, please, forgive me about the noise
and I'd gently ask about directions for a more appropriated discussion
group.

First of all, let me me introduce myself and provide some context that I
think it may be useful to evaluate the proposal. I'm Javier Fernandez,
from Igalia. I've been working in the last months to implement a
refactoring to move the Custom Handlers code from //chrome to a new
//component (there is a breakout session [1] in BlinOn15 and lighting
talk [2] in BlinkOn16 if anybody is interested). One of the goals of
this refactoring was to allow Chrome embedders to reuse the Custom
Handler codebase that was originally defined as an intrinsic part of
chrome. The proposal I'd like to discuss now is just another step on
this direction.

The idea I want to discuss is to allow the SchemeRegistry to handle a
new list of schemes, for which embedders (or even chrome flavors like
ChromeOS) could add predefined custom handlers at compile time. I've
written an explainer [3] to describe this proposal, which I tried to
keep simple and concise; I'll be willing to elaborate it and provide a
design doc, if needed. 

The SchemeRegistry class is defined in the ContentClient public API,
that's why I considered this the appropriated forum to discuss the
proposal, but I believe it'd need some integration with the //url layer,
so we may need to include someone else in the loop.

Thanks,
Javi

[1] https://youtu.be/kHIN6FkLAS8
[2] https://youtu.be/o1pJJuQiCmQ?t=2771
[3]
https://github.com/Igalia/explainers/blob/main/custom-protocol-handlers/PredefinedHandlers/README.md

[Javier Fernandez]

+embedder-dev