Decouple contrast boost from fake gamma.

src/ports/SkFontHost_mac.cpp

Index: src/ports/SkFontHost_mac.cpp
diff --git a/src/ports/SkFontHost_mac.cpp b/src/ports/SkFontHost_mac.cpp
index 53d5610575b1f4867a7ae13188823a0b78bb4dbf..1a81c7a3f3df19fe2080961a4d9582583687f1d5 100644
--- a/src/ports/SkFontHost_mac.cpp
+++ b/src/ports/SkFontHost_mac.cpp
@@ -2030,7 +2030,8 @@ void SkTypeface_Mac::onFilterRec(SkScalerContextRec* rec) const {
     // All other masks can use regular gamma.
     if (SkMask::kA8_Format == rec->fMaskFormat && SkPaint::kNo_Hinting == hinting) {
 #ifndef SK_GAMMA_APPLY_TO_A8
-        rec->ignorePreBlend();
+        // SRGBTODO: Is this correct?
+        rec->ignorePreBlend(false);
 #endif
     } else {
         //CoreGraphics dialates smoothed text as needed.