Remove unused 3DTransformedDescendant methods.

Neither of these methods appear to be getting called.

BUG=260898

Review URL: https://codereview.chromium.org/138713002

git-svn-id: svn://svn.chromium.org/blink/trunk@165119 bbb929c8-8fbe-4397-9dbb-9b2b20218538