use colortype instead of config

include/core/SkImageInfo.h

Index: include/core/SkImageInfo.h
diff --git a/include/core/SkImageInfo.h b/include/core/SkImageInfo.h
index 2b449dc2132cf029ddfa2c6ec7b2991b532b5317..1c73d959af54d55852516ca369bd933591a22655 100644
--- a/include/core/SkImageInfo.h
+++ b/include/core/SkImageInfo.h
@@ -165,6 +165,13 @@ struct SkImageInfo {
         return info;
     }
 
+    static SkImageInfo MakeUnknown(int width, int height) {
+        SkImageInfo info = {
+            width, height, kUnknown_SkColorType, kIgnore_SkAlphaType
+        };
+        return info;
+    }
+
     int width() const { return fWidth; }
     int height() const { return fHeight; }
     SkColorType colorType() const { return fColorType; }