[SVG] SVGLength{,List} migration to new SVG property impl.

This CL replaces SVG{Animated,}Length{,List} classes with NewSVGProperty implementation.

For details, see design doc: https://docs.google.com/document/d/1bg7CUyUszqdwmENY3JX6_PoQD6uHRCNcRPJMlC4qlkw/edit?usp=sharing

BUG=308818

Review URL: https://codereview.chromium.org/112003003

git-svn-id: svn://svn.chromium.org/blink/trunk@164832 bbb929c8-8fbe-4397-9dbb-9b2b20218538