Poor implementation of Path.approximate()

Include a very poor implementation of Path.approximate() in LayoutLib
that only returns the first and last coordinate of the path. This avoids
crashing the rendering when certain assumptions are made on the value
returned from the method.

Also change the error to a warning.

Change-Id: I9241dec734d4df90a9eebd1e6de8b3e443eee3c8