encoding/jsonpb: change MarshalOptions.Compact option to Indent

This makes it consistent with jsonpb.MarshalOptions. This does change
the default to be in compact form.

Change-Id: I1b07f06f282c019b30f3f1cbb43f6c8cba18f385
Reviewed-on: https://go-review.googlesource.com/c/protobuf/+/168405
Reviewed-by: Joe Tsai <thebrokentoaster@gmail.com>
diff --git a/encoding/textpb/encode_test.go b/encoding/textpb/encode_test.go
index 6a6cd7a..b2fed47 100644
--- a/encoding/textpb/encode_test.go
+++ b/encoding/textpb/encode_test.go
@@ -1111,7 +1111,8 @@
 	for _, tt := range tests {
 		tt := tt
 		t.Run(tt.desc, func(t *testing.T) {
-			t.Parallel()
+			// Use 2-space indentation on all MarshalOptions.
+			tt.mo.Indent = "  "
 			b, err := tt.mo.Marshal(tt.input)
 			if err != nil && !tt.wantErr {
 				t.Errorf("Marshal() returned error: %v\n", err)