Introduce toSVGSMILElement, and use it

As a step to change static_cast with toSVGXXX, static_cast<SVGSMILElement*> can
be changed with toSVGSMILElement().

BUG=

Review URL: https://chromiumcodereview.appspot.com/19798009

git-svn-id: svn://svn.chromium.org/blink/trunk@155048 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Remove border shorthand special case for generator

The borderShorthand special case in StylePropertyShorthand appears to
be needed due to using a 2D array instead of a regular array, but it is
only used as a regular array when constructing the StylePropertyShorthand
static local object.

BUG=

Review URL: https://chromiumcodereview.appspot.com/19967009

git-svn-id: svn://svn.chromium.org/blink/trunk@155049 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Make DOMImplementation::hasFeature() behave according to specification

Make DOMImplementation::hasFeature() behave according to the latest specification:
http://dom.spec.whatwg.org/#dom-domimplementation-hasfeature

Specifically, the function now returns true unconditionally for any non-SVG feature.
This behavior is consistent with Firefox.

hasFeature() originally would report whether the user agent claimed to support a
given DOM feature, but experience proved it was not nearly as reliable or granular
as simply checking whether the desired interfaces, attributes, or methods existed.
As such, it should no longer be used, but continues to exist (and simply returns
true) so that old pages don't stop working.

BUG=264683

Review URL: https://chromiumcodereview.appspot.com/20738002

git-svn-id: svn://svn.chromium.org/blink/trunk@155050 bbb929c8-8fbe-4397-9dbb-9b2b20218538