CloudMade/Leaflet — pull request #733 by aparshin (2012-06-16 14:26:19+00:00)
Title: Add tile layer with polygonal boundary

It is implementation of tile vector layer with arbitrary polygonal boundary using HTML5 Canvas for clipping tiles. Polygons with holes and multipolygons are also supported. Usage example is also added.

Maybe, it is good candidate for a plugin, but I've found no information about them...