Clean up SVGNames usage in core/rendering

Clean up SVGNames usage in core/rendering, sometimes the header is included but it is not used.
In some other spots, prefer "using namespace SVG".

BUG=

Review URL: https://codereview.chromium.org/332773002

git-svn-id: svn://svn.chromium.org/blink/trunk@176049 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Simplified code for styleResolverChanged.

Removed StyleResolverChange class by:

- Marking Document scope for recalc in the stylesheet collection class like
  we do for shadow scopes instead of propagating it up to Document.

- Move the check for doing full repaint after all stylesheets have been
  loaded to Document::styleResolverChanged.

Introduced a shouldUpdateDocumentStyleSheetCollection helper method.

R=esprehn@chromium.org,ojan@chromium.org

Review URL: https://codereview.chromium.org/330043002

git-svn-id: svn://svn.chromium.org/blink/trunk@176050 bbb929c8-8fbe-4397-9dbb-9b2b20218538