Reset SVGAnimationElement values animation state on attribute changes

If the animation element is moved in the DOM, and it is a 'values'
animation, then m_lastValuesAnimation{From,To} would not be reset, which
could mean that if the current from/to values matched those prior to the
move (reinsertion), calculateFromAndtoValues would not be called, and
the SVGAnimateElement::m_{from,to}Type values would not be initialized,
and hence cause a crash when trying to compute the animated value.

BUG=329822

Review URL: https://codereview.chromium.org/107083007

git-svn-id: svn://svn.chromium.org/blink/trunk@164599 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Remove unused method - previousSkippingChildrenPostOrder - from NodeTraversal.h

BUG=331880

Review URL: https://codereview.chromium.org/122373004

git-svn-id: svn://svn.chromium.org/blink/trunk@164600 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Use default argument value instead of overloading for MarkupAccumulator::serializeNodes()

The last argument to MarkupAccumulator::serializeNodes() was optional and we were dealing
with this using overloads instead of having a default value for the last argument. This
makes the code a bit cleaner / shorter.

R=adamk
BUG=None

Review URL: https://codereview.chromium.org/111443014

git-svn-id: svn://svn.chromium.org/blink/trunk@164601 bbb929c8-8fbe-4397-9dbb-9b2b20218538