Separate HarfBuzz/Uniscribe functionality in FontPlatformDataWin

Selectively compile either the HarfBuzz or Uniscribe support functions
for FontPlatformDataWin. This helps ensure that we use either one or
the other for everything and reduces the binary size.

BUG=251355, 313423

Review URL: https://codereview.chromium.org/61333002

git-svn-id: svn://svn.chromium.org/blink/trunk@161414 bbb929c8-8fbe-4397-9dbb-9b2b20218538