Revert "Merge FontPlatformDataHarfBuzz into FontPlatformData"

This reverts commit 44cef15dcdbf3b78339c3678fe533f3a97e59870.

The patch were reverted due to problem with uninitialized memory.

BUG=413229
TBR= jianli@chromium.org,  dominik.rottsches@intel.com

Review URL: https://codereview.chromium.org/557823003

git-svn-id: svn://svn.chromium.org/blink/trunk@181824 bbb929c8-8fbe-4397-9dbb-9b2b20218538