openlayers/ol3 — pull request #793 by ahocevar (2013-06-17 13:29:33+00:00)
Title: Making extent optional for projections

The projection validity extent is used to generate a sensible set of default resolutions and a sensible default tile grid. By making it optional, we can still generate defaults - with zoom levels that are similar to the default web mercator zoom levels (based on fitting the world on a single tile, even if the projection is not available for the whole world).