Implement Symbol correctly in dart2js.

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

Index: dart/sdk/lib/_internal/compiler/implementation/compiler.dart
diff --git a/dart/sdk/lib/_internal/compiler/implementation/compiler.dart b/dart/sdk/lib/_internal/compiler/implementation/compiler.dart
index 93fd69cce8f4b4cf7a0478ec2b4480eb127528be..f2f887a13bb7107187d15272df8a09d704c1e4a8 100644
--- a/dart/sdk/lib/_internal/compiler/implementation/compiler.dart
+++ b/dart/sdk/lib/_internal/compiler/implementation/compiler.dart
@@ -306,6 +306,11 @@ abstract class Compiler implements DiagnosticListener {
   ClassElement listClass;
   ClassElement typeClass;
   ClassElement mapClass;
+  ClassElement symbolClass;
+  FunctionElement symbolConstructor;
+  ClassElement mirrorSystemClass;
+  FunctionElement mirrorSystemGetNameFunction;
+
   ClassElement jsInvocationMirrorClass;
   /// Document class from dart:mirrors.
   ClassElement documentClass;
@@ -616,6 +621,19 @@ abstract class Compiler implements DiagnosticListener {
         library.addToScope(dynamicClass, this);
       });
     }
+    if (uri == Uri.parse('dart:mirrors')) {
+      mirrorSystemClass = library.find(const SourceString('MirrorSystem'));
+      print(mirrorSystemClass);
+    }
+  }
+
+  void onClassResolved(ClassElement cls) {
+    if (mirrorSystemClass == cls) {
+      mirrorSystemGetNameFunction =
+        cls.lookupLocalMember(const SourceString('getName'));
+    } else if (symbolClass == cls) {
+      symbolConstructor = cls.constructors.head;
+    }
   }
 
   LibraryElement scanBuiltinLibrary(String filename);
@@ -645,6 +663,11 @@ abstract class Compiler implements DiagnosticListener {
           '$missingCoreClasses');
     }
 
+    // The following classes may not exist.
+    // TODO(ahe): It is possible that we have to require the presence
+    // of Symbol as we change how we implement noSuchMethod.
+    symbolClass = lookupCoreClass('Symbol');
+
     final List missingHelperClasses = [];
     ClassElement lookupHelperClass(String name) {
       ClassElement result = jsHelperLibrary.find(new SourceString(name));
@@ -1013,6 +1036,14 @@ abstract class Compiler implements DiagnosticListener {
                   api.Diagnostic.ERROR);
   }
 
+  // TODO(ahe): Rename to reportWarning when that method has been removed.
+  void reportWarningCode(Spannable node, MessageKind errorCode,
+                         [Map arguments = const {}]) {
+    reportMessage(spanFromSpannable(node),
+                  errorCode.error(arguments),
+                  api.Diagnostic.WARNING);
+  }
+
   void reportMessage(SourceSpan span, Diagnostic message, api.Diagnostic kind) {
     // TODO(ahe): The names Diagnostic and api.Diagnostic are in
     // conflict. Fix it.