Dummy DDC implementation of MirrorSystem

pkg/dev_compiler/tool/input_sdk/private/js_mirrors.dart

Index: pkg/dev_compiler/tool/input_sdk/private/js_mirrors.dart
diff --git a/pkg/dev_compiler/tool/input_sdk/private/js_mirrors.dart b/pkg/dev_compiler/tool/input_sdk/private/js_mirrors.dart
index 1a6f26d8ac84d07897f405f94d7fd501c3b465ef..a6b0ac3ce70e227e831a0323f6a599edd4e506b1 100644
--- a/pkg/dev_compiler/tool/input_sdk/private/js_mirrors.dart
+++ b/pkg/dev_compiler/tool/input_sdk/private/js_mirrors.dart
@@ -19,8 +19,7 @@ String getName(Symbol symbol) {
 Symbol getSymbol(name, library) =>
     throw new UnimplementedError("MirrorSystem.getSymbol unimplemented");
 
-final currentJsMirrorSystem = throw new UnimplementedError(
-    "MirrorSystem.currentJsMirrorSystem unimplemented");
+final currentJsMirrorSystem = new JsMirrorSystem();
 
 final _typeMirror = JS('', 'Symbol("_typeMirror")');
 
@@ -225,6 +224,14 @@ dynamic _toJsMap(Map<Symbol, dynamic> map) {
   return obj;
 }
 
+class JsMirrorSystem implements MirrorSystem {
+  get libraries => const {};
+
+  noSuchMethod(Invocation i) {
+    _unimplemented(this.runtimeType, i);
+  }
+}
+
 class JsMirror implements Mirror {
   noSuchMethod(Invocation i) {
     _unimplemented(this.runtimeType, i);