Disable SVG Fonts in CSS on all platforms except GDI Windows (XP, Vista)

This patch disables SVG fonts everywhere except GDI platforms, per [1].
The patch itself is straightforward: the SVGFontsOnNonGDIPlatforms
runtime enabled feature has been added but is disabled by default.

TestExpectations has been updated with the usual mass of rebaselines.
coords-dom-02-f.svg has been marked as no longer failing.

A brand new test has been added to test the fallback code. This test is
marked as failing on XP (we have no Vista bots).

[1] https://groups.google.com/a/chromium.org/d/msg/blink-dev/pYbbUcYvlYY/LQvFvM8KZZEJ

BUG=242735

Review URL: https://codereview.chromium.org/360203002

git-svn-id: svn://svn.chromium.org/blink/trunk@177785 bbb929c8-8fbe-4397-9dbb-9b2b20218538