Concept of how dart:mirrors LibraryMirror, ClassMirror can be implemented in dart2js.

sdk/lib/_internal/compiler/implementation/compiler.dart

Index: sdk/lib/_internal/compiler/implementation/compiler.dart
diff --git a/sdk/lib/_internal/compiler/implementation/compiler.dart b/sdk/lib/_internal/compiler/implementation/compiler.dart
index 636fcc530952bc44532781cfc2215c708c93adf1..5d4178b25d735ea4cd4182436de7948809686456 100644
--- a/sdk/lib/_internal/compiler/implementation/compiler.dart
+++ b/sdk/lib/_internal/compiler/implementation/compiler.dart
@@ -134,6 +134,7 @@ abstract class Compiler implements DiagnosticListener {
   LibraryElement coreLibrary;
   LibraryElement isolateLibrary;
   LibraryElement isolateHelperLibrary;
+  LibraryElement mirrorsLibrary;
   LibraryElement jsHelperLibrary;
   LibraryElement interceptorsLibrary;
   LibraryElement foreignLibrary;
@@ -218,6 +219,8 @@ abstract class Compiler implements DiagnosticListener {
   static const SourceString RUNTIME_TYPE = const SourceString('runtimeType');
   static const SourceString START_ROOT_ISOLATE =
       const SourceString('startRootIsolate');
+  static const SourceString CREATE_MIRROR_SYSTEM =
+      const SourceString('_createMirrorSystem');
   bool enabledNoSuchMethod = false;
   bool enabledRuntimeType = false;
   bool enabledFunctionApply = false;
@@ -421,6 +424,16 @@ abstract class Compiler implements DiagnosticListener {
 
   bool hasIsolateSupport() => isolateLibrary != null;
 
+  void enableMirrorsSupport(LibraryElement element) {
+    mirrorsLibrary = element.patch;
+    enqueuer.resolution.addToWorkList(
+        mirrorsLibrary.find(CREATE_MIRROR_SYSTEM));
+    enqueuer.codegen.addToWorkList(
+        mirrorsLibrary.find(CREATE_MIRROR_SYSTEM));
+  }
+
+  bool hasMirrorsSupport() => mirrorsLibrary != null;
+
   /**
    * This method is called before [library] import and export scopes have been
    * set up.