Fold SVGAnimatedTypeAnimator into SVGAnimateElement

This folds the functionality of SVGAnimatedTypeAnimator, mostly
verbatim, into SVGAnimateElement. Some methods are renamed, and a new
interface is defined, which allows <animateTransform> to be more
isolated from the rest of the <animate> implementation.
SVGAnimateElement::m_animatedProperty is renamed to m_animatedValue, and
SVGAnimatedTypeAnimator::m_animatedProperty is renamed to
m_targetProperty.
Dial down or remove some asserts in favor of other asserts.

BUG=641437

Review-Url: https://codereview.chromium.org/2595393002
Cr-Commit-Position: refs/heads/master@{#440613}
8 files changed