Add intrinsicSize attribute to SVGImageElement

Design doc: https://docs.google.com/document/d/1yh_-ayeaFV0EjuR51U641zbrPAB0Baqj6UrC9bT9iqQ/edit#heading=h.y7amr11fn0tb

This CL implements "intrinsicSize" attribute to SVGImageElement. This
attribute has been added to HTMLImageElement and HTMLVideoElement.
The value of "intrinsicSize" overrides the intrinsic size:

1. When no width and height is specified, the value of "intrinsicSize"
specifies the <svg:image> element's layout size.
2. When one dimension is specified, the value of "intrinsicSize" is
used as an aspect ratio to determine the other dimension.
3. If both width and height are specified, "intrinsicSize" has no
effect.

Bug: 874629
Cq-Include-Trybots: luci.chromium.try:linux_layout_tests_slimming_paint_v2;master.tryserver.blink:linux_trusty_blink_rel
Change-Id: I9023d6cf7a818c983155efc12505f1d6fd18de43
Reviewed-on: https://chromium-review.googlesource.com/1210544
Reviewed-by: Steve Kobes <skobes@chromium.org>
Commit-Queue: Luna Lu <loonybear@chromium.org>
Cr-Commit-Position: refs/heads/master@{#590065}
11 files changed