Gate subpixel scaling by RuntimeEnabledFeatures::subpixelFontScalingEnabled() on Mac

Source/platform/fonts/mac/SimpleFontDataMac.mm

Index: Source/platform/fonts/mac/SimpleFontDataMac.mm
diff --git a/Source/platform/fonts/mac/SimpleFontDataMac.mm b/Source/platform/fonts/mac/SimpleFontDataMac.mm
index 5586030251754e8d0c7decee790aa8ca5e11a5d7..ee6ac00f00cbac9bc8a03ab729b10ad99f53b883 100644
--- a/Source/platform/fonts/mac/SimpleFontDataMac.mm
+++ b/Source/platform/fonts/mac/SimpleFontDataMac.mm
@@ -31,6 +31,8 @@
 #import <ApplicationServices/ApplicationServices.h>
 #import <float.h>
 #import <unicode/uchar.h>
+#import "RuntimeEnabledFeatures.h"
+#import "platform/LayoutTestSupport.h"
 #import "platform/SharedBuffer.h"
 #import "platform/fonts/Font.h"
 #import "platform/fonts/FontCache.h"
@@ -106,6 +108,14 @@ static NSString *webFallbackFontFamily(void)
     return webFallbackFontFamily.get();
 }
 
+static bool useHinting()
+{
+    // Enable hinting when subpixel font scaling is disabled or
+    // when running the set of standard non-subpixel layout tests,
+    // otherwise use subpixel glyph positioning.
+    return (isRunningLayoutTest() && !isFontAntialiasingEnabledForTest()) || !RuntimeEnabledFeatures::subpixelFontScalingEnabled();
+}
+
 const SimpleFontData* SimpleFontData::getCompositeFontReferenceFontData(NSFont *key) const
 {
     if (key && !CFEqual(RetainPtr<CFStringRef>(AdoptCF, CTFontCopyPostScriptName(CTFontRef(key))).get(), CFSTR("LastResort"))) {
@@ -315,9 +325,8 @@ PassRefPtr<SimpleFontData> SimpleFontData::platformCreateScaledFontData(const Fo
     float size = m_platformData.size() * scaleFactor;
     FontPlatformData scaledFontData([[NSFontManager sharedFontManager] convertFont:m_platformData.font() toSize:size], size, false, false, m_platformData.orientation());
 
-    // Until we replace AppKit API (NSFontManager etc.), we always want to disable hinting,
-    // so we use the printerFont here.
-    scaledFontData.setFont([scaledFontData.font() printerFont]);
+    // AppKit forgets about hinting property when scaling, so we have to remind it.
+    scaledFontData.setFont(useHinting() ? [scaledFontData.font() screenFont] : [scaledFontData.font() printerFont]);

[Dominik Röttsches, 2014/05/28 14:33:51]

This part should have been in the previous patch for removing
setUsePrinterFont() removal.

 
     if (scaledFontData.font()) {
         NSFontManager *fontManager = [NSFontManager sharedFontManager];