Returns the bounding rectangle of the edge chain that connects the
vertices defined so far. This bound satisfies the guarantee made
above, i.e. if the edge chain defines a loop, then the bound contains
the S2LatLng coordinates of all S2Points contained by the loop.
Returns the bounding rectangle of the edge chain that connects the vertices defined so far. This bound satisfies the guarantee made above, i.e. if the edge chain defines a loop, then the bound contains the S2LatLng coordinates of all S2Points contained by the loop.