Fix text axis alignment calculation

BUG=skia:

Review URL: https://codereview.chromium.org/1405583002
diff --git a/src/core/SkScalerContext.cpp b/src/core/SkScalerContext.cpp
index 35a9b29..29f794a 100644
--- a/src/core/SkScalerContext.cpp
+++ b/src/core/SkScalerContext.cpp
@@ -829,7 +829,7 @@
     if (0 == matrix[SkMatrix::kMSkewY]) {
         return kX_SkAxisAlignment;
     }
-    if (0 == matrix[SkMatrix::kMScaleX]) {
+    if (0 == matrix[SkMatrix::kMSkewX]) {
         return kY_SkAxisAlignment;
     }
     return kNone_SkAxisAlignment;