Allow small-caps synthesis for @font-face with multiple sources including SVG format

Since small-caps synthesis is not supported for SVG fonts, our font
matching algorithm ignored @font-faces that have svg sources when
small-caps variant is requested. This behavior had a problem that it
discards @font-face even if non-svg (ex. woff) source is available.

This patch moves that SVG-font check to CSSSegmentedFontFace::getFontData()
so that it skips SVG fonts only when SVG source is used.

BUG=298970
TEST=fast/css,svg/*

Review URL: https://codereview.chromium.org/26702008

git-svn-id: svn://svn.chromium.org/blink/trunk@159429 bbb929c8-8fbe-4397-9dbb-9b2b20218538