Revert of Revert of Remove Mac native font type members from FontPlatformData

Revert of Revert of Remove Mac native font type members from FontPlatformData (patchset #1 id:1 of https://codereview.chromium.org/1021483004/)

Reason for revert:
Loislo and Dominik handled this in a better way. For some reason, the "cancel commit" didn't work (or /me didn't).

Original issue's description:
> Revert of Remove Mac native font type members from FontPlatformData (patchset #11 id:200001 of https://codereview.chromium.org/879533003/)
> 
> Reason for revert:
> The patch broke the Mac GN builder, preventing the roll:
> 
> ERROR at //third_party/WebKit/Source/platform/BUILD.gn:221:7: Item not found
>       "fonts/skia/FontCustomPlatformDataSkia.cpp",
> 
> It may have also caused some failures on Mac.
> 
> Original issue's description:
> > Remove Mac native font type members from FontPlatformData
> > 
> > FontPlatformData keeps several Mac specific font members 
> > around, NSFont, ctFont, cgFont, while all other platforms
> > rely on just using an SkTypeface. This leads to a lot of 
> > ifdefs in the code, confusion about which member is currently
> > instantiated and a history of null-dereference crashes on Mac
> > due to hard to track failures of font instantiation.
> > 
> > After we got access to a CTFont object from an
> > SkTypeface for compatibility with HarfBuzz AAT shaping and
> > clipboard text export [1], I suggest to remove the native 
> > handles and focus on using SkTypefaces. This allows us as 
> > well to remove a lot of mostly redundant platform-specific
> > code on Mac.
> > 
> > [1] https://codereview.chromium.org/872963003/
> > 
> > BUG=414234
> > 
> > Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=192506
> 
> TBR=eae@chromium.org,rsesek@chromium.org,kbr@chromium.org,japhet@chromium.org,pfeldman@chromium.org,tkent@chromium.org,alph@chromium.org,dominik.rottsches@intel.com
> NOPRESUBMIT=true
> NOTREECHECKS=true
> NOTRY=true
> BUG=414234
> 
> Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=192544

TBR=eae@chromium.org,rsesek@chromium.org,kbr@chromium.org,japhet@chromium.org,pfeldman@chromium.org,tkent@chromium.org,alph@chromium.org,dominik.rottsches@intel.com
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=414234
Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=192545

[Julien - ping for review, 2015-03-25 15:51:02]

Created Revert of Revert of Remove Mac native font type members from
FontPlatformData

[commit-bot: I haz the power, 2015-03-25 15:51:19]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1022663004/1

[commit-bot: I haz the power, 2015-03-25 15:52:01]

Committed patchset #1 (id:1) as
https://src.chromium.org/viewvc/blink?view=rev&revision=192545