Should CropTarget generation be limited to SecureContext?

[youennf]

Current API is limiting CropTarget generation to SecureContext.
I wonder why this is the case, CropTarget does not qualify as a powerful feature.
I do not see a wide use of CropTarget generation in non secure context (except for mixed content), maybe in the future if a non secure page is captured by a secured page.
Is there any other reason than new API == SecureContext?