[SVG] Remove AnimatedNewProperty enum value. Use original type values.

"AnimatedNewProperty" was used to indicate types migrated to new property implementation. However, it turns out that enum representing real type is required when handling "SMIL animations animating CSS values". In addition, they are useful when validating downcasts.

This patch reverts addition of AnimatedNewProperty, and now NewSVGProperty implementations also use original type values.

BUG=308818
TBR=pdr@chromium.org

Review URL: https://codereview.chromium.org/121013003

git-svn-id: svn://svn.chromium.org/blink/trunk@164326 bbb929c8-8fbe-4397-9dbb-9b2b20218538