Adaptive UI: conditionally hide controls?

[Malvoz]

Similarly (and related to) to #216, this issue relates to the following use case: Maps4HTML/HTML-Map-Element-UseCases-Requirements#174.

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Controls may be unavailable to the user if they don't happen to fit the size of the map viewer.

Should they be hidden in that case? That's what browsers seem to do for controls that don't fit in media elements.