Reland "Share code between FontPlatformDataWin and FontPlatformDataHarfBuzz"

Move linux specific code from FontPlatformDataHarfBuzz.cpp into a new
FontPlatformDataLinux.cpp file and merge the shared code across the win
and linux implementations into FontPlatformDataHarfBuzz.cpp.

With this change code shared across all HarfBuzz platforms is in
FontPlatformDataHarfBuzz.cpp and platform specific code in the Linux and
Windows files respectively.

Once Mac is fully moved over to HarfBuzz FontPlatformDataHarfBuzz will
be renamed to FontPlatformData and moved to platform/fonts.

Originally landed as r170801 and reverted as r170805 due to an android
build failure.

TBR=dglazkov@chromium.org

Review URL: https://codereview.chromium.org/224763004

git-svn-id: svn://svn.chromium.org/blink/trunk@170834 bbb929c8-8fbe-4397-9dbb-9b2b20218538