Create an antialiased virtual layout test group for font testing on Mac

Source/platform/fonts/mac/FontMac.cpp

Index: Source/platform/fonts/mac/FontMac.cpp
diff --git a/Source/platform/fonts/mac/FontMac.cpp b/Source/platform/fonts/mac/FontMac.cpp
index 94340a12ff50c6e71a0acc55776b222a6261abde..80df9806aafa3e4451dfdd946b1dc91a75092e2c 100644
--- a/Source/platform/fonts/mac/FontMac.cpp
+++ b/Source/platform/fonts/mac/FontMac.cpp
@@ -105,7 +105,8 @@ void Font::drawGlyphs(GraphicsContext* gc, const SimpleFontData* font,
 
     if (isRunningLayoutTest()) {
         shouldSmoothFonts = false;
-        shouldAntialias = false;
+        if (!isFontSmoothingEnabledForTest())

[Dirk Pranke, 2014/04/23 19:25:48]

I guess we're just re-using existing function names here, but this is confusing.
Can you say something like

shouldAntialias = shouldAntialias && isAntiAliasingEnabledForTest() 

and change the names? If you can't change the names, perhaps at least add a
comment about why isFontSmoothingEnabled() affects anti-aliasing but not font
smoothing :).

+            shouldAntialias = false;
     }
 
     const GlyphBufferGlyph* glyphs = glyphBuffer.glyphs(from);