PSA: New Custom Handlers component

[Javier Fernandez]

Hi,

This email is just to announce that most of the Protocol Handler logic,
which was originally integrated in //chrome, has been moved to
//components to a new component called Custom Handlers [1].

The idea of this component is to allow embedders to reuse this Protocol
Handler logic to define their own features and protocol related
policies. For now, only Chrome uses the component through the
ProtocolHandlerRegistryFactory [2] and the
ChromeProtocolHandlerRegistryDelegate [3] classes, but I have plans to
start working as soon as possible on implementing support for the
ContentShell. This would allow us to define Web Platform Tests for the
protocol handler related features; although we may need to implement
some additional APIs [4] for the WPT tools.

I'd like to use this announcement to ask for volunteers to be listed in
the OWNERS file of the new component. As I said, all the codebase of the
new component has been in //chrome for several years now, so I think
it'd be better if we could have owners with experience on the Protocol
Handler logic.

I've submitted a CL [5] to add a README.md with some basic documentation
(reviews and suggestions are more than welcome) and  the OWNERS file for
the new component.

Regards.

[1]
https://source.chromium.org/chromium/chromium/src/+/main:components/custom_handlers/
[2]
https://cs.chromium.org/search?q=file:/protocol_handler_registry_factory.h$
[3]
https://cs.chromium.org/search?q=file:/chrome_protocol_handler_registry_delegate.h$
[4] https://github.com/web-platform-tests/wpt/issues/26819
[5] https://chromium-review.googlesource.com/c/chromium/src/+/3497435