Guard for null typefaces in Mac system font instantiation

The previous change [1] to always apply opsz to Mac system fonts did not
handle a situation in which loading a system font comes back with a null
result. Cover this case for the base typeface as well as for the case
where instantiating the variable font fails.

[1] https://chromium-review.googlesource.com/c/chromium/src/+/2020767

Bug: 1049391
Change-Id: I2aad15c31f7ad793abc389f66afab3fbdf963df7
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2041667Reviewed-by: Ben Wagner <bungeman@chromium.org>
Commit-Queue: Dominik Röttsches <drott@chromium.org>
Cr-Commit-Position: refs/heads/master@{#739391}

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

@@ -224,6 +224,9 @@ scoped_refptr<SimpleFontData> FontCache::PlatformFallbackFontForCharacter(
       platform_data.Orientation(), font_description.FontOpticalSizing(),
       nullptr);  // No variation paramaters in fallback.
 
+  if (!alternate_font)
+    return nullptr;
+
   return FontDataFromFontPlatformData(alternate_font.get(), kDoNotRetain);
 }
 
@@ -297,7 +300,7 @@ std::unique_ptr<FontPlatformData> FontCache::CreateFontPlatformData(
       platform_font, size, synthetic_bold, synthetic_italic,
       font_description.Orientation(), font_description.FontOpticalSizing(),
       font_description.VariationSettings());
-  if (!platform_data->Typeface()) {
+  if (!platform_data || !platform_data->Typeface()) {
     return nullptr;
   }
   return platform_data;

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

@@ -151,6 +151,9 @@ std::unique_ptr<FontPlatformData> FontPlatformDataFromNSFont(
   if (!valid_configured_axes && optical_sizing == kNoneOpticalSizing)
     return make_typeface_fontplatformdata();
 
+  if (!typeface)
+    return nullptr;
+
   int existing_axes = typeface->getVariationDesignPosition(nullptr, 0);
   // Don't apply variation parameters if the font does not have axes or we
   // fail to retrieve the existing ones.
@@ -196,9 +199,14 @@ std::unique_ptr<FontPlatformData> FontPlatformDataFromNSFont(
   SkFontArguments::VariationPosition variation_design_position{
       coordinates_to_set.data(), coordinates_to_set.size()};
 
-  typeface = typeface->makeClone(
-      SkFontArguments().setVariationDesignPosition(variation_design_position));
+  sk_sp<SkTypeface> cloned_typeface(typeface->makeClone(
+      SkFontArguments().setVariationDesignPosition(variation_design_position)));
 
+  if (!cloned_typeface) {
+    // Applying varition parameters failed, return original typeface.
+    return make_typeface_fontplatformdata();
+  }
+  typeface = cloned_typeface;
   return make_typeface_fontplatformdata();
 }