Remove Mac native font type members from FontPlatformData

Source/web/mac/WebSubstringUtil.mm

Index: Source/web/mac/WebSubstringUtil.mm
diff --git a/Source/web/mac/WebSubstringUtil.mm b/Source/web/mac/WebSubstringUtil.mm
index 2b726f046891d9de12ac8b6d5764bd658f30f3c1..36c33da37c048e7b5567a1c46698da9a883594d3 100644
--- a/Source/web/mac/WebSubstringUtil.mm
+++ b/Source/web/mac/WebSubstringUtil.mm
@@ -78,7 +78,8 @@ static NSAttributedString* attributedSubstringFromRange(const Range* range)
             continue;
 
         RenderStyle* style = renderer->style();
-        NSFont* font = style->font().primaryFont()->getNSFont();
+        // TODO(dro): Check whether we can really use the CTFont here.
+        const NSFont* font = style->font().primaryFont()->getNSFont();
         // If the platform font can't be loaded, it's likely that the site is
         // using a web font. For now, just use the default font instead.
         // TODO(rsesek): Change the font activation flags to allow other processes