Stop testing variable system fonts on macOS 10.11.

Support for variable fonts on macOS earlier than 10.12 was incomplete.
CGFonts supported variations fairly well by themselves, but hid the tag
name of the axes. CTFonts only supported named variations of system fonts
(which meant only Skia). It is possible to create a CTFont from a
CGFont, but this can into various bugs (because the CTFont didn't really
know about the variations in the CGFont). Beginning in 10.12 it is
possible to create a CTFont from data and set a variation on it directly,
allowing for much simpler code, a path forward for better and faster
API, and a possible reduction in font data leaking.

The only real observable affect of this change will be that the Skia
system font on macOS 10.11 will stop varying. Blink will still use
FreeType to render variable webfonts on macOS 10.10 and 10.11.

Change-Id: I7c188f4245af1b36c6e258a17935710a1ac02076
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1937778
Commit-Queue: Ben Wagner <bungeman@chromium.org>
Commit-Queue: Dominik Röttsches <drott@chromium.org>
Reviewed-by: Dominik Röttsches <drott@chromium.org>
Cr-Commit-Position: refs/heads/master@{#719413}

third_party/blink/web_tests/NeverFixTests

@@ -286,10 +286,11 @@ crbug.com/551843 [ Linux ] virtual/text-antialias/fallback-traits-fixup.html [ S
 crbug.com/551843 [ Linux ] virtual/text-antialias/emoji-font-weight-mac.html [ Skip ]
 crbug.com/551843 [ Win ] virtual/text-antialias/emoji-font-weight-mac.html [ Skip ]
 
-# Variable system font only supported on Mac atm.
+# Variable system font only supported on Mac 10.12 and newer atm.
 crbug.com/670246 [ Linux ] virtual/text-antialias/variable-fonts/variable-mac-system-font.html [ Skip ]
 crbug.com/670246 [ Win ] virtual/text-antialias/variable-fonts/variable-mac-system-font.html [ Skip ]
 crbug.com/670246 [ Mac10.10 ] virtual/text-antialias/variable-fonts/variable-mac-system-font.html [ Skip ]
+crbug.com/670246 [ Mac10.11 ] virtual/text-antialias/variable-fonts/variable-mac-system-font.html [ Skip ]
 
 # prefer_compositing_to_lcd_text causes things to get composited regardless of their opaqueness, causing the test to fail
 crbug.com/381840 virtual/prefer_compositing_to_lcd_text/compositing/overflow/overflow-scroll-background-opaque-to-transparent.html [ Skip ]