Parse SVG as HTML

This change switches the SVG parser to be the HTML parser all the time. This
work is being done behind a flag to guage the potential compat risk.

BUG=243882
R=abarth@chromium.org

Review URL: https://codereview.chromium.org/15796009

git-svn-id: svn://svn.chromium.org/blink/trunk@151572 bbb929c8-8fbe-4397-9dbb-9b2b20218538
11 files changed