Two arrow heads for polyline arrow material

Run the polyline Sandcastle example, switch to Columbus view, and zoom in on the polyline with the arrow material. On AMD at least, I see two arrows:


Start by running the polyline Sandcastle example, switch to Columbus view, and zoom in on the polyline using the arrow material, reproducing the duplicate arrow heads reported on AMD. Trace the rendering path for that example and material; done means the polyline displays one arrow head in the affected view and the regression is covered by an appropriate test if the project provides one.

Written by the indexing model from the issue text.