[SVG] Refactor static buffered-rendering using display lists.

Instead of caching an ImageBuffer, use a display list
representation for RenderSVGImage buffered-rendering=static,
to avoid record-time rasterization.

BUG=426451
TEST=svg/repaint/buffered-rendering-static-image.html
R=fs@opera.com,pdr@chromium.org,schenney@chromium.org

Review URL: https://codereview.chromium.org/691383002

git-svn-id: svn://svn.chromium.org/blink/trunk@184738 bbb929c8-8fbe-4397-9dbb-9b2b20218538