Add oblique as a slant.

Some fonts have italic and oblique in the same family, see

http://lucidafonts.com/fonts/family/lucida-sans
http://www.gust.org.pl/projects/e-foundry/latin-modern

GOLD_TRYBOT_URL= https://gold.skia.org/search2?unt=true&query=source_type%3Dgm&master=false&issue=1921903002

Chromium side change at https://crrev.com/1921503006/ .

Review-Url: https://codereview.chromium.org/1921903002
diff --git a/src/ports/SkFontHost_mac.cpp b/src/ports/SkFontHost_mac.cpp
index 02c5464..72d4690 100644
--- a/src/ports/SkFontHost_mac.cpp
+++ b/src/ports/SkFontHost_mac.cpp
@@ -417,7 +417,7 @@
     return SkFontStyle(unit_weight_to_fontstyle(weight),
                        unit_width_to_fontstyle(width),
                        slant ? SkFontStyle::kItalic_Slant
-                       : SkFontStyle::kUpright_Slant);
+                             : SkFontStyle::kUpright_Slant);
 }
 
 #define WEIGHT_THRESHOLD    ((SkFontStyle::kNormal_Weight + SkFontStyle::kBold_Weight)/2)
@@ -2151,7 +2151,7 @@
 static int compute_metric(const SkFontStyle& a, const SkFontStyle& b) {
     return sqr(a.weight() - b.weight()) +
            sqr((a.width() - b.width()) * 100) +
-           sqr((a.isItalic() != b.isItalic()) * 900);
+           sqr((a.slant() != b.slant()) * 900);
 }
 
 static SkTypeface* createFromDesc(CTFontDescriptorRef desc) {