Don't allow <stop> as layout tree child of <svg> or <g>

LayoutSVGGradientStop would be allowed as children of <svg>, <g> and
other containers which could trigger asserts and wreck havoc.

BUG=466937

Review URL: https://codereview.chromium.org/1009923002

git-svn-id: svn://svn.chromium.org/blink/trunk@191932 bbb929c8-8fbe-4397-9dbb-9b2b20218538
6 files changed
tree: d50a84a730de09f5d842d6a7eff137b048f741fb
  1. third_party/