Remove mirrors in product mode

runtime/vm/parser.cc

Index: runtime/vm/parser.cc
diff --git a/runtime/vm/parser.cc b/runtime/vm/parser.cc
index 048c1845fe65f1c8c6582179add48a0e3803fe5d..81a78a450d2b6cd600f9f1eaecb1ac6a08f4a233 100644
--- a/runtime/vm/parser.cc
+++ b/runtime/vm/parser.cc
@@ -42,8 +42,6 @@
 namespace dart {
 
 DEFINE_FLAG(bool, enable_debug_break, false, "Allow use of break \"message\".");
-DEFINE_FLAG(bool, enable_mirrors, true,
-    "Disable to make importing dart:mirrors an error.");
 DEFINE_FLAG(bool, load_deferred_eagerly, false,
     "Load deferred libraries eagerly.");
 DEFINE_FLAG(bool, trace_parser, false, "Trace parser operations.");
@@ -14335,8 +14333,6 @@ void Parser::SkipQualIdent() {
 
 namespace dart {
 
-DEFINE_FLAG(bool, enable_mirrors, true,
-    "Disable to make importing dart:mirrors an error.");
 DEFINE_FLAG(bool, load_deferred_eagerly, false,
     "Load deferred libraries eagerly.");
 DEFINE_FLAG(bool, link_natives_lazily, false, "Link native calls lazily");