[SVG] Draw SVGImage patterns using DisplayListPattern

Refactor SVGImage::drawPatternForContainer() to avoid record time
rasterization. Use display list shaders instead.

Also add a test for SVG image background-repeat coverage (previously
missing).

R=fs@opera.com,pdr@chromium.org,schenney@chromium.org
BUG=426451

Review URL: https://codereview.chromium.org/674023003

git-svn-id: svn://svn.chromium.org/blink/trunk@184387 bbb929c8-8fbe-4397-9dbb-9b2b20218538