[Font Load Events] Respect "text" parameters of FontFaceSet methods

The match(), load(), and check() methods of FontFaceSet take a string
argument that can be used to select only font-faces those unicode-range
intersects the given characters.
This patch implements the above behavior.

BUG=53213
TEST=fast/css

Review URL: https://codereview.chromium.org/26432003

git-svn-id: svn://svn.chromium.org/blink/trunk@159243 bbb929c8-8fbe-4397-9dbb-9b2b20218538