Don't call FormAssociatedElement::validity() internally

This saves the malloc cost and the memory usage of the ValidityState
object which just proxys all methods back to the form control. Calling
it internally doesn't make sense.

This saves 19.5k of memory usage on squished presidents which has 10k form
controls and 0.2% of the recalcStyle cost. 1.4% of the recalcStyle time on
that page is spent in malloc, we should drive it down as far as possible.

Review URL: https://codereview.chromium.org/25076008

git-svn-id: svn://svn.chromium.org/blink/trunk@158579 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Move the resizer logic to RenderLayerScrollableArea

BUG=260899

Review URL: https://codereview.chromium.org/25140002

git-svn-id: svn://svn.chromium.org/blink/trunk@158580 bbb929c8-8fbe-4397-9dbb-9b2b20218538