Replace Thinkness with Thickness.

The FontMetricsFlags::kUnderlineThinknessIsValid_Flag has a typo in it.
Fortunately no user currently uses this enumeration value by name but
instead uses the getter so the name can be updated.

BUG=skia:6174

Change-Id: I810260d826482de1da8876cd9739d24b3bfb0f95
Reviewed-on: https://skia-review.googlesource.com/10050
Reviewed-by: Cary Clark <caryclark@google.com>
Commit-Queue: Ben Wagner <bungeman@google.com>
diff --git a/src/ports/SkFontHost_mac.cpp b/src/ports/SkFontHost_mac.cpp
index a9b8ccd..ca236a3 100644
--- a/src/ports/SkFontHost_mac.cpp
+++ b/src/ports/SkFontHost_mac.cpp
@@ -1306,7 +1306,7 @@
     metrics->fUnderlineThickness = CGToScalar( CTFontGetUnderlineThickness(fCTFont.get()));
     metrics->fUnderlinePosition = -CGToScalar( CTFontGetUnderlinePosition(fCTFont.get()));
 
-    metrics->fFlags |= SkPaint::FontMetrics::kUnderlineThinknessIsValid_Flag;
+    metrics->fFlags |= SkPaint::FontMetrics::kUnderlineThicknessIsValid_Flag;
     metrics->fFlags |= SkPaint::FontMetrics::kUnderlinePositionIsValid_Flag;
 
     // See https://bugs.chromium.org/p/skia/issues/detail?id=6203