Revert "Merge FontPlatformDataHarfBuzz and FontPlatformData headers"

This reverts commit 72f392cc147764ec75e4f5db1667b60c6bdf1815.

fast/css/font-face-zero-hash-key.html is crashing on WebKit Mac10.7 (dbg)

BUG=None
TBR=eae, dominik.rottsches@intel.com

Review URL: https://codereview.chromium.org/535073004

git-svn-id: svn://svn.chromium.org/blink/trunk@181345 bbb929c8-8fbe-4397-9dbb-9b2b20218538