Add a pref to indicate user intent to enter webxr

[asajeffrey]

Add a pref to indicate that the user has indicated intent to enter webxr.

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• ./mach build -d does not report any errors
• ./mach test-tidy does not report any errors
• These changes do not require tests because it's a command-line pref

[highfive]

Heads up! This PR modifies the following files:

• @KiChjang: components/script/dom/xrsystem.rs

[highfive]

Warning

• These commits modify script code, but no tests are modified. Please consider adding a test!

[asajeffrey]

This needs thought about a bit, because it's switching off a security feature. It's needed for scenarios where we're launching straight into webxr, for example from the gstreamer plugin, which has no 2d view. With this pref we can enter hubs using

./mach run -r "https://hubs.mozilla.com/$ROOM_ID?no_force_webvr&vr_entry_type=vr_now" --pref dom.gamepad.enabled --pref dom.svg.enabled --pref dom.webrtc.enabled --pref dom.canvas_capture.enabled --pref dom.webrtc.transceiver.enabled --pref dom.webxr.user-intent

[asajeffrey]

@avadacatavra you may have opinions about ^

[Manishearth]

Perhaps we should name the pref something scarier? idk. Implementation seems fine by me.

[asajeffrey]

Yeah, I tried to think of an appropriate dom.webxr.you-really-need-to-know-what-youre-doing-here pref name.

[Manishearth]

override_user_intent?

[Manishearth]

maybe stick an _unsafe in there

[asajeffrey]

assume_user_intent?

[Manishearth]

Yeah, but unsafe_assume_user_intent

[asajeffrey]

We have a winner!

[asajeffrey]

Renamed the pref. @Manishearth ok'd setting the pref in the gstreamer plugin at https://chat.mozilla.org/#/room/#servo:mozilla.org/$3DTiFVKWr85K322xn49tTBoMtEOvScTFtqi4o5okyA4

@bors-servo r=Manishearth

[bors-servo]

📌 Commit 89a2c51 has been approved by Manishearth

[bors-servo]

⌛ Testing commit 89a2c51 with merge c26a803...

[bors-servo]

☀️ Test successful - status-taskcluster
Approved by: Manishearth
Pushing c26a803 to master...