HTMLSelectElement should not override childShouldCreateRenderer

Instead the two renderers it creates should reject children with
isChildAllowed(). Even that's a hack though, we should use a ShadowRoot
with insertion points in the future but we can't do that yet because
too many things break.

This and https://codereview.chromium.org/125203004/ leave only
HTMLMediaElement overriding childShouldCreateRenderer outside of
SVG. A future patch will remove that override too.

Review URL: https://codereview.chromium.org/118723006

git-svn-id: svn://svn.chromium.org/blink/trunk@164676 bbb929c8-8fbe-4397-9dbb-9b2b20218538