[SVGDom] Expose intrinsic size info

[SVGDom] Expose intrinsic size info

  * expose intrinsic size info on <svg> nodes.

  * tweak the SkSVGDOM constructor to no longer take an container size
    param, but instead default to intrinsic size
  * update clients to call SkSVGDOM::setContainerSize() explicitly, when
    needed

R=robertphillips@google.com,stephana@google.com
GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2345533002

Review-Url: https://codereview.chromium.org/2345533002