Check for characters the same way we draw them with Skia on Windows.

This method seems closer to the way we actually draw,
should be just as fast, and doesn't require us to nail down
how Skia is going to treat bitmap fonts and scaling.



git-svn-id: svn://svn.chromium.org/blink/trunk@156715 bbb929c8-8fbe-4397-9dbb-9b2b20218538