Remove includes of RenderSVGResource.h where it's not used

Some additional unused includes nearby also bite the dust.

BUG=420022

Review URL: https://codereview.chromium.org/666143003

git-svn-id: svn://svn.chromium.org/blink/trunk@184091 bbb929c8-8fbe-4397-9dbb-9b2b20218538