Add SkTPin.

include/core/SkScalar.h

Index: include/core/SkScalar.h
diff --git a/include/core/SkScalar.h b/include/core/SkScalar.h
index fae23eb23a6c9a9b7862c215a41fb9f5ec4841d7..443454a2efc4805d6d3a738175e29abc210d5f61 100644
--- a/include/core/SkScalar.h
+++ b/include/core/SkScalar.h
@@ -175,9 +175,7 @@ static inline SkScalar SkScalarClampMax(SkScalar x, SkScalar max) {
 }
 
 static inline SkScalar SkScalarPin(SkScalar x, SkScalar min, SkScalar max) {
-    x = SkTMin(x, max);
-    x = SkTMax(x, min);
-    return x;
+    return SkTPin(x, min, max);
 }
 
 SkScalar SkScalarSinCos(SkScalar radians, SkScalar* cosValue);