Reland 2: mac: Use a placeholder string for the family name of the system font.

Source/core/layout/LayoutThemeMac.mm

Index: Source/core/layout/LayoutThemeMac.mm
diff --git a/Source/core/layout/LayoutThemeMac.mm b/Source/core/layout/LayoutThemeMac.mm
index 507401a54c330e01c516e1c3b519c2e217e4f3e7..9e761bd8211e40d1782a51b9648ffd3e32350635 100644
--- a/Source/core/layout/LayoutThemeMac.mm
+++ b/Source/core/layout/LayoutThemeMac.mm
@@ -238,7 +238,7 @@ void LayoutThemeMac::systemFont(CSSValueID systemFontID, FontStyle& fontStyle, F
     fontStyle = ([fontManager traitsOfFont:font] & NSItalicFontMask) ? FontStyleItalic : FontStyleNormal;
     fontWeight = toFontWeight([fontManager weightOfFont:font]);
     fontSize = [font pointSize];
-    fontFamily = [font webCoreFamilyName];
+    fontFamily = @"BlinkMacSystemFont";
 }
 
 static RGBA32 convertNSColorToColor(NSColor *color)
@@ -592,7 +592,7 @@ void LayoutThemeMac::setFontFromControlSize(ComputedStyle& style, NSControlSize
     fontDescription.setGenericFamily(FontDescription::SerifFamily);
 
     NSFont* font = [NSFont systemFontOfSize:[NSFont systemFontSizeForControlSize:controlSize]];
-    fontDescription.firstFamily().setFamily([font webCoreFamilyName]);
+    fontDescription.firstFamily().setFamily(@"BlinkMacSystemFont");
     fontDescription.setComputedSize([font pointSize] * style.effectiveZoom());
     fontDescription.setSpecifiedSize([font pointSize] * style.effectiveZoom());