proto: fix signature of UnmarshalState and MarshalState

The pseudo-internal MarshalState and UnmarshalState method should
not have a seperate Message argument since it is passed in through
the extensible MarshalInput and UnmarshalInput values.

Change-Id: I838aadaee30e91cdf888ab024e65348c73c1cd7e
Reviewed-on: https://go-review.googlesource.com/c/protobuf/+/222678
Reviewed-by: Damien Neil <dneil@google.com>
diff --git a/internal/impl/codec_field.go b/internal/impl/codec_field.go
index 6204e65..f9b6836 100644
--- a/internal/impl/codec_field.go
+++ b/internal/impl/codec_field.go
@@ -278,8 +278,9 @@
 	if n < 0 {
 		return out, wire.ParseError(n)
 	}
-	o, err := opts.Options().UnmarshalState(m, piface.UnmarshalInput{
-		Buf: v,
+	o, err := opts.Options().UnmarshalState(piface.UnmarshalInput{
+		Buf:     v,
+		Message: m.ProtoReflect(),
 	})
 	if err != nil {
 		return out, err
@@ -421,8 +422,9 @@
 	if n < 0 {
 		return out, wire.ParseError(n)
 	}
-	o, err := opts.Options().UnmarshalState(m, piface.UnmarshalInput{
-		Buf: b,
+	o, err := opts.Options().UnmarshalState(piface.UnmarshalInput{
+		Buf:     b,
+		Message: m.ProtoReflect(),
 	})
 	if err != nil {
 		return out, err
@@ -551,8 +553,9 @@
 		return out, wire.ParseError(n)
 	}
 	mp := reflect.New(goType.Elem())
-	o, err := opts.Options().UnmarshalState(asMessage(mp), piface.UnmarshalInput{
-		Buf: v,
+	o, err := opts.Options().UnmarshalState(piface.UnmarshalInput{
+		Buf:     v,
+		Message: asMessage(mp).ProtoReflect(),
 	})
 	if err != nil {
 		return out, err
@@ -613,8 +616,9 @@
 		return pref.Value{}, out, wire.ParseError(n)
 	}
 	m := list.NewElement()
-	o, err := opts.Options().UnmarshalState(m.Message().Interface(), piface.UnmarshalInput{
-		Buf: v,
+	o, err := opts.Options().UnmarshalState(piface.UnmarshalInput{
+		Buf:     v,
+		Message: m.Message(),
 	})
 	if err != nil {
 		return pref.Value{}, out, err
@@ -680,8 +684,9 @@
 		return pref.Value{}, out, wire.ParseError(n)
 	}
 	m := list.NewElement()
-	o, err := opts.Options().UnmarshalState(m.Message().Interface(), piface.UnmarshalInput{
-		Buf: b,
+	o, err := opts.Options().UnmarshalState(piface.UnmarshalInput{
+		Buf:     b,
+		Message: m.Message(),
 	})
 	if err != nil {
 		return pref.Value{}, out, err
@@ -765,8 +770,9 @@
 		return out, wire.ParseError(n)
 	}
 	mp := reflect.New(goType.Elem())
-	o, err := opts.Options().UnmarshalState(asMessage(mp), piface.UnmarshalInput{
-		Buf: b,
+	o, err := opts.Options().UnmarshalState(piface.UnmarshalInput{
+		Buf:     b,
+		Message: asMessage(mp).ProtoReflect(),
 	})
 	if err != nil {
 		return out, err