Fix product build

runtime/vm/dev_fs.cc

Index: runtime/vm/dev_fs.cc
diff --git a/runtime/vm/dev_fs.cc b/runtime/vm/dev_fs.cc
index 0ad6b0d3040fa988778f5fa64e64b08a1be3c93a..afbb23b91d3c0a9b579163bd29541f5a6055bf7c 100644
--- a/runtime/vm/dev_fs.cc
+++ b/runtime/vm/dev_fs.cc
@@ -16,6 +16,8 @@
 
 namespace dart {
 
+#ifndef PRODUCT
+
 static const uint8_t decode_table[256] = {
   64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64,
   64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64,
@@ -368,4 +370,6 @@ void DevFS::ReadFile(JSONStream* js,
                           file_contents->size());
 }
 
+#endif  // !PRODUCT
+
 }  // namespace dart