[Cocoa] Support WOFF2

[Cocoa] Support WOFF2
https://bugs.webkit.org/show_bug.cgi?id=150830

Reviewed by Zalan Bujtas.

Source/WebCore:

On platforms which support it, WebKit only needs to recognize WOFF2.

Test: fast/text/woff2.html

* platform/graphics/mac/FontCustomPlatformData.cpp:
(WebCore::FontCustomPlatformData::supportsFormat):

LayoutTests:

* platform/mac/TestExpectations: Disable the test on Operating Systems which don't support WOFF2.
* fast/text/resources/ahem.woff2: Added.
* fast/text/woff2-expected.html: Added.
* fast/text/woff2.html: Added.

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@191934 268f45cc-cd09-0410-ab3c-d52691b4dbfc