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

Synchronise releasing / default activating this feature with the other platforms.

BUG=378195
R=eae,dglazkov,eseidel

Review URL: https://codereview.chromium.org/304723002

git-svn-id: svn://svn.chromium.org/blink/trunk@175203 bbb929c8-8fbe-4397-9dbb-9b2b20218538

third_party/WebKit/Source/platform/fonts/mac/FontCacheMac.mm

@@ -31,6 +31,7 @@
 #import "platform/fonts/FontCache.h"
 
 #import <AppKit/AppKit.h>
+#import "RuntimeEnabledFeatures.h"
 #import "platform/LayoutTestSupport.h"
 #import "platform/fonts/FontDescription.h"
 #import "platform/fonts/FontPlatformData.h"
@@ -65,6 +66,14 @@ static void fontCacheRegisteredFontsChangedNotificationCallback(CFNotificationCe
     invalidateFontCache(0);
 }
 
+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();
+}
+
 void FontCache::platformInit()
 {
     CFNotificationCenterAddObserver(CFNotificationCenterGetLocalCenter(), this, fontCacheRegisteredFontsChangedNotificationCallback, kCTFontManagerRegisteredFontsChangedNotification, 0, CFNotificationSuspensionBehaviorDeliverImmediately);
@@ -161,10 +170,7 @@ PassRefPtr<SimpleFontData> FontCache::platformFallbackForCharacter(const FontDes
         }
     }
 
-    // Enable hinting, which is equivalent to using the screen font,
-    // only when running the set of standard non-subpixel layout tests,
-    // otherwise use subpixel glyph positioning.
-    substituteFont = !isRunningLayoutTest() || isFontAntialiasingEnabledForTest() ? [substituteFont printerFont] : [substituteFont screenFont];
+    substituteFont = useHinting() ? [substituteFont screenFont] : [substituteFont printerFont];
 
     substituteFontTraits = [fontManager traitsOfFont:substituteFont];
     substituteFontWeight = [fontManager weightOfFont:substituteFont];
@@ -211,10 +217,7 @@ FontPlatformData* FontCache::createFontPlatformData(const FontDescription& fontD
         actualTraits = [fontManager traitsOfFont:nsFont];
     NSInteger actualWeight = [fontManager weightOfFont:nsFont];
 
-    // Enable hinting, which is equivalent to using the screen font,
-    // only when running the set of standard non-subpixel layout tests,
-    // otherwise use subpixel glyph positioning.
-    NSFont *platformFont = !isRunningLayoutTest() || isFontAntialiasingEnabledForTest() ? [nsFont printerFont] : [nsFont screenFont];
+    NSFont *platformFont = useHinting() ? [nsFont screenFont] : [nsFont printerFont];
     bool syntheticBold = (isAppKitFontWeightBold(weight) && !isAppKitFontWeightBold(actualWeight)) || fontDescription.isSyntheticBold();
     bool syntheticOblique = ((traits & NSFontItalicTrait) && !(actualTraits & NSFontItalicTrait)) || fontDescription.isSyntheticItalic();
 

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