Initial error handling code

include/core/SkUnitMapper.h

Index: include/core/SkUnitMapper.h
diff --git a/include/core/SkUnitMapper.h b/include/core/SkUnitMapper.h
index 754be26841353e227f3dcad7f3bb93b4e288ad76..0aa881e7be83679468c25c82ae0859adc742cea4 100644
--- a/include/core/SkUnitMapper.h
+++ b/include/core/SkUnitMapper.h
@@ -16,6 +16,8 @@
 #include "SkFlattenable.h"
 
 class SkUnitMapper : public SkFlattenable {
+    typedef SkFlattenable INHERITED;
+
 public:
     SK_DECLARE_INST_COUNT(SkUnitMapper)
 
@@ -25,11 +27,10 @@ public:
     */
     virtual uint16_t mapUnit16(uint16_t x) = 0;
 
+    SK_DEFINE_FLATTENABLE_TYPE(SkUnitMapper)
+
 protected:
     SkUnitMapper(SkFlattenableReadBuffer& rb) : SkFlattenable(rb) {}
-
-private:
-    typedef SkFlattenable INHERITED;
 };
 
 #endif