HD export in Firefox of large objects has seams

Firefox creates seams along the Tile lines if a Stamp is made large enough, has Custom Shadow, and has any changes made to Advanced Color Settings.

h Steps to reproduce

• Select the Stamp Tool and open the catalog

• Select a Stamp with Custom Shadow (Dead Trees work well for this)

• Open the Advanced Settings and change a Color value (like Hue)

• Place a Stamp

• Increase Size so the Stamp covers most of the canvas

• HD Export

Expected: The Stamp should render as it is in the scene.

Actual: The Stamp's shadow doesn't render over the Tile lines properly.