Bug 215992

While investigating https://bugs.webkit.org/show_bug.cgi?id=215981, one failure was in the generation of NavigatorMediaDevices.idl which currently looks like:

[
    Conditional=MEDIA_STREAM,
    EnabledAtRuntime=MediaDevices,
] partial interface Navigator {
    [SameObject, SecureContext, ContextAllowsMediaDevices] readonly attribute MediaDevices mediaDevices;
    [Custom, EnabledBySetting=LegacyGetUserMedia] undefined getUserMedia(object constraints, object? successCallback, object? errorCallback);
};

One thing to note here is that the extended attributes on the partial interface declaration itself (Conditional=MEDIA_STREAM and EnabledAtRuntime=MediaDevices) are really shorthand for mapping those extended attributes to all the member properties.

In the mentioned bug, I want to change the partial interface wide "EnabledAtRuntime=MediaDevices" to "EnabledBySetting=MediaDevices", which maps the EnabledBySetting to each member of the partial interface. The issue is that the code generator currently overwrites "EnabledBySetting=LegacyGetUserMedia" on the getUserMedia operation, but really it would make more sense to merge them.

This seems to be a general problem for many potentially mergeable extended attributes, we already kind of merge "Conditional" extended attributes, but only for operations for some reason.