[SVGDom] Fix href handling for radial gradients

Currently, the href logic only visits linear gradient nodes.  Update to
also visit radial gradients, per
https://www.w3.org/TR/SVG/pservers.html#RadialGradientElementHrefAttribute.
Change-Id: I8d33d9faa65dae776c13e134c497acccfb428abb
Reviewed-on: https://skia-review.googlesource.com/57480
Commit-Queue: Robert Phillips <robertphillips@google.com>
Reviewed-by: Robert Phillips <robertphillips@google.com>
1 file changed