Add pattern matchers for SkRecord

src/utils/SkTLogic.h

Index: src/utils/SkTLogic.h
diff --git a/src/utils/SkTLogic.h b/src/utils/SkTLogic.h
index 62952ad13c267d88e911a34a25a34cebc2bd5835..925d4bdcd4fb3d514d0197f10d5815165aa120e6 100644
--- a/src/utils/SkTLogic.h
+++ b/src/utils/SkTLogic.h
@@ -89,4 +89,14 @@ public:
     static const bool value = sizeof(func<Derived>(NULL)) == sizeof(uint16_t);      \
 }
 
+// Same sort of thing as SK_CREATE_MEMBER_DETECTOR, but checks for the existence of a nested type.
+#define SK_CREATE_TYPE_DETECTOR(type)                                   \
+template <typename T>                                                   \
+class HasType_##type {                                                  \
+    template <typename U> static uint8_t func(typename U::type*);       \
+    template <typename U> static uint16_t func(...);                    \
+public:                                                                 \
+    static const bool value = sizeof(func<T>(NULL)) == sizeof(uint8_t); \
+}
+
 #endif