implement the HTML5 pointer lock API

[Cris Dywan]

The internet archive just released a collection of Win 3.1 games, using the DosBox emulator to run them on the website. On Chrome this triggers a "Allow/Deny archive.org to disable your mouse cursor" popup. Games are only playable using mouse or touch after accepting this.
In the browser app/ Oxide there's no such popup and mouse input doesn't work.

https://archive.org/details/win3_Mono3Dlx

Another (more lightweight) example page: https://mdn.github.io/pointer-lock-demo/

[Olivier Tilloy (osomon)]

This requires to implement the HTML5 pointer lock API in oxide (https://developer.mozilla.org/en-US/docs/Web/API/Pointer_Lock_API).

[Olivier Tilloy (osomon)]

content::WebContentsDelegate::RequestToLockMouse(…) and content::WebContentsDelegate::LostMouseLock() need to be overridden in oxide::WebView (and ask the user to allow pointer lock), and oxide::RenderWidgetHostView::LockMouse() and oxide::RenderWidgetHostView::UnlockMouse() need to be implemented to do the work to actually hide/show the mouse cursor (we might want to have a look at how it’s implemented in RenderWidgetHostViewAura in chromium).

[Olivier Tilloy (osomon)]

With a dummy implementation of the above (that silently accepts the pointer lock requests), I verified that https://mdn.github.io/pointer-lock-demo/ works.