Improve type checking in ol.geom.flat
Improve type checking in ol.geom.simplify
Improve type checking in ol.color.fromString
Always use goog.vec.Mat4.Number instead of goog.vec.Mat.AnyType
Use assertInstanceof instead of getVectorLayer
Use assertInstanceof instead of getVectorSource
Merge pull request #1463 from twpayne/vector-api-type-fixes

[vector-api] Type checking improvements