GMSMapPointInterpolate
extern GMSMapPoint GMSMapPointInterpolate(GMSMapPoint a, GMSMapPoint b,
double t)Returns a linearly interpolated point on the segment [a, b], at the fraction t from a. t==0
corresponds to a, t==1 corresponds to b.
The interpolation takes place along the short path between the points potentially crossing the date line. E.g. interpolating from San Francisco to Tokyo will pass north of Hawaii and cross the date line.