diff --git a/build/config/compiler/BUILD.gn b/build/config/compiler/BUILD.gn
index bf5820945f4566..0bcd7f45b80bc9 100644
--- a/build/config/compiler/BUILD.gn
+++ b/build/config/compiler/BUILD.gn
@@ -1884,6 +1884,8 @@ config("default_warnings") {
 
           # TODO(https://crbug.com/1490607): Fix and re-enable.
           "-Wno-thread-safety-reference-return",
+
+          "-Wno-c++11-narrowing-const-reference",
         ]
       }
     }
diff --git a/third_party/blink/renderer/platform/fonts/mac/font_matcher_mac.h b/third_party/blink/renderer/platform/fonts/mac/font_matcher_mac.h
index 2345ef0c9bfb35..f05255bae76483 100644
--- a/third_party/blink/renderer/platform/fonts/mac/font_matcher_mac.h
+++ b/third_party/blink/renderer/platform/fonts/mac/font_matcher_mac.h
@@ -56,6 +56,12 @@ base::apple::ScopedCFTypeRef<CTFontRef> MatchSystemUIFont(
 // Converts a blink::FontSelectionValue to the nearest AppKit font weight if
 // possible, otherwise returns the default font weight.
 int ToAppKitFontWeight(FontSelectionValue);
+
+PLATFORM_EXPORT
+int ToCSSFontWeight(float ct_font_weight);
+
+float ToCTFontWeight(int css_weight);
+
 }  // namespace blink
 
 #endif  // THIRD_PARTY_BLINK_RENDERER_PLATFORM_FONTS_MAC_FONT_MATCHER_MAC_H_
diff --git a/third_party/blink/renderer/platform/fonts/mac/font_matcher_mac.mm b/third_party/blink/renderer/platform/fonts/mac/font_matcher_mac.mm
index f80070e2a1c595..321bebdf5c4ab9 100644
--- a/third_party/blink/renderer/platform/fonts/mac/font_matcher_mac.mm
+++ b/third_party/blink/renderer/platform/fonts/mac/font_matcher_mac.mm
@@ -108,6 +108,22 @@ BOOL BetterChoice(NSFontTraitMask desired_traits,
   return candidate_weight_delta_magnitude < chosen_weight_delta_magnitude;
 }
 
+NSFontWeight ToFontWeight(blink::FontSelectionValue font_weight) {
+  if (font_weight <= 50 || font_weight >= 950) {
+    return NSFontWeightRegular;
+  }
+
+  const NSFontWeight ns_font_weights[] = {
+      NSFontWeightUltraLight, NSFontWeightThin,   NSFontWeightLight,
+      NSFontWeightRegular,    NSFontWeightMedium, NSFontWeightSemibold,
+      NSFontWeightBold,       NSFontWeightHeavy,  NSFontWeightBlack,
+  };
+  size_t select_weight = roundf(font_weight / 100) - 1;
+  DCHECK_GE(select_weight, 0ul);
+  DCHECK_LE(select_weight, std::size(ns_font_weights));
+  return ns_font_weights[select_weight];
+}
+
 }  // namespace
 
 ScopedCFTypeRef<CTFontRef> MatchUniqueFont(const AtomicString& unique_font_name,
@@ -145,6 +161,9 @@ void ClampVariationValuesToFontAcceptableRange(
     FontSelectionValue& weight,
     FontSelectionValue& width) {
   ScopedCFTypeRef<CFArrayRef> all_axes(CTFontCopyVariationAxes(ct_font.get()));
+  if (!all_axes) {
+    return;
+  }
   for (CFIndex i = 0; i < CFArrayGetCount(all_axes.get()); ++i) {
     CFDictionaryRef axis = base::apple::CFCast<CFDictionaryRef>(
         CFArrayGetValueAtIndex(all_axes.get(), i));