Enveloped tree

Purpose: This test cases is the reverse of the promoted subtree case. As time containers are defined relative to the outermost SVG document fragment this case tests that when an outermost <svg> fragment is added as a child of another svg document fragment, the animations behave correctly and the time containers are resolved correctly.

Operation: There are two animations that are more-or-less identical except for a few aesthetic features. Both contain a circle that moves to the right. After 1.5s the second document fragment (on the right) is removed and added as a child of the first document fragment.

Expected results: The circles move right. Once they reach about the half-way point the second document disappears and the circle is overlayed onto the first animation. The two circles continue moving. They should have the same horizontal position at all times.