SVGRenderTreeAsText cleanup/code sharing.

        No test changes, only code cleanup.

        * rendering/RenderText.cpp:
        (WebCore::RenderText::firstRunOrigin):
        * rendering/RenderText.h:
        * rendering/SVGRenderTreeAsText.cpp:
        (WebCore::writeStandardPrefix):
        (WebCore::writeChildren):
        (WebCore::write):
        (WebCore::writeRenderResources):

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@42803 268f45cc-cd09-0410-ab3c-d52691b4dbfc