Bug 1260454. Disable LCD font smoothing if we have grayscale AA on OS X. r=lsalzman

gfx/2d/DrawTargetSkia.cpp

@@ -636,8 +636,10 @@ DrawTargetSkia::FillGlyphs(ScaledFont *aFont,
     // SkFontHost_cairo does not support subpixel text, so only enable it for other font hosts.
     paint.mPaint.setSubpixelText(true);
 
-    if (aFont->GetType() == FontType::MAC && shouldLCDRenderText) {
+    if (aFont->GetType() == FontType::MAC) {
       // SkFontHost_mac only supports subpixel antialiasing when hinting is turned off.
+      // For grayscale AA, we want to disable font smoothing as the only time we should
+      // use grayscale AA is with explicit -moz-osx-font-smoothing
       paint.mPaint.setHinting(SkPaint::kNo_Hinting);
     } else {
       paint.mPaint.setHinting(SkPaint::kNormal_Hinting);