Revert "Revert 157959 "Introduce a new reference graph to SVG*TearOffs.""

Reland the patches. All known SVGProperty memory bugs were resolved.

BUG=270000
BUG=294464

TBR=pdr@chromium.org,haraken@chromium.org,inferno@chromium.org

Review URL: https://codereview.chromium.org/25461003

git-svn-id: svn://svn.chromium.org/blink/trunk@158679 bbb929c8-8fbe-4397-9dbb-9b2b20218538