Partial revert of r174548: Make several functions in SVGRenderSupport templated for performance

Partial revert of r174548: Make several functions in SVGRenderSupport templated
for performance. This is an speculative attempt to fix a crash in
WebCore::SVGRenderSupport::computeContainerBoundingBoxes<WebCore::RenderSVGRoot>().

R=pdr@chromium.org
BUG=382428

Review URL: https://codereview.chromium.org/323043005

git-svn-id: svn://svn.chromium.org/blink/trunk@175955 bbb929c8-8fbe-4397-9dbb-9b2b20218538