dart2js: Support const symbols in the startup emitter.

pkg/compiler/lib/src/js_emitter/startup_emitter/fragment_emitter.dart

Index: pkg/compiler/lib/src/js_emitter/startup_emitter/fragment_emitter.dart
diff --git a/pkg/compiler/lib/src/js_emitter/startup_emitter/fragment_emitter.dart b/pkg/compiler/lib/src/js_emitter/startup_emitter/fragment_emitter.dart
index 5bf5d697a34a4e36dea5227f55bbe321e2f75aaa..1eaaa8029015aed45aa77496d9c40fc9f6618d56 100644
--- a/pkg/compiler/lib/src/js_emitter/startup_emitter/fragment_emitter.dart
+++ b/pkg/compiler/lib/src/js_emitter/startup_emitter/fragment_emitter.dart
@@ -1120,10 +1120,17 @@ class FragmentEmitter {
 
     globals.add(emitMangledGlobalNames());
 
-    // The [MANGLED_NAMES] table is only relevant for reflection.
-    // TODO(floitsch): verify that this is correct.
-    globals.add(new js.Property(js.string(MANGLED_NAMES),
-                                new js.ObjectInitializer([])));
+    // The [MANGLED_NAMES] table must contain the mapping for const symbols.
+    // Without const symbols, the table is only relevant for reflection and
+    // therefore unused in this emitter.
+    List<js.Property> mangledNamesProperties = <js.Property>[];
+    program.symbolsMap.forEach((js.Name mangledName, String unmangledName) {
+      mangledNamesProperties.add(
+          new js.Property(mangledName, js.string(unmangledName)));
+    });
+    globals.add(new js.Property(
+        js.string(MANGLED_NAMES),
+        new js.ObjectInitializer(mangledNamesProperties)));
 
     globals.add(emitGetTypeFromName());