Always apply opsz variable font axis optical sizing

When font-optical-sizing: is set to auto (the default) do apply a value
to the opsz axis even if font-variation-settings is not explicitly
specified.

TEST: virtual/text-antialias/mac-system-ui-trak.html
Bug: 1005969
Change-Id: I4baf448c6bc465b98eda4cf2538f3ef48e9c5ef1
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2020767
Commit-Queue: Ben Wagner <bungeman@chromium.org>
Reviewed-by: Ben Wagner <bungeman@chromium.org>
Cr-Commit-Position: refs/heads/master@{#735406}

third_party/blink/renderer/platform/fonts/mac/font_platform_data_mac.mm

@@ -148,7 +148,7 @@ std::unique_ptr<FontPlatformData> FontPlatformDataFromNSFont(
           : 0;
 
   // No variable font requested, return static font.
-  if (!valid_configured_axes)
+  if (!valid_configured_axes && optical_sizing == kNoneOpticalSizing)
     return make_typeface_fontplatformdata();
 
   int existing_axes = typeface->getVariationDesignPosition(nullptr, 0);
@@ -171,7 +171,7 @@ std::unique_ptr<FontPlatformData> FontPlatformDataFromNSFont(
   for (auto& coordinate : coordinates_to_set) {
     // Set opsz to font size but allow having it overriden by
     // font-variation-settings in case it has 'opsz'.
-    if (coordinate.axis == kOpszTag) {
+    if (coordinate.axis == kOpszTag && optical_sizing == kAutoOpticalSizing) {
       if (coordinate.value != SkFloatToScalar(size)) {
         coordinate.value = SkFloatToScalar(size);
         axes_reconfigured = true;