Throw when reflecting on elements not covered by a `MirrorsUsed` annotation.

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

Index: sdk/lib/_internal/compiler/implementation/js_backend/backend.dart
diff --git a/sdk/lib/_internal/compiler/implementation/js_backend/backend.dart b/sdk/lib/_internal/compiler/implementation/js_backend/backend.dart
index 8b6f8725ad2f945ae4b9170ad68dae3e29f9da01..03de46dea3c0d40ecc84ba8879a83539e0aa3ca3 100644
--- a/sdk/lib/_internal/compiler/implementation/js_backend/backend.dart
+++ b/sdk/lib/_internal/compiler/implementation/js_backend/backend.dart
@@ -1555,6 +1555,13 @@ class JavaScriptBackend extends Backend {
     if (metaTargets != null) metaTargetsUsed.addAll(metaTargets);
   }
 
+  /// Returns `true` if [element] can be accessed through reflection, that is,
+  /// is in the set of elements covered by a `MirrorsUsed` annotation.

[ngeoffray, 2013/08/29 07:45:49]

Please also add a comment for isNeededForReflection. It is not obvious what the
difference is between the 2.

[karlklose, 2013/08/29 15:33:37]

Done.

+  bool isAccessibleByReflection(Element element) {
+    if (hasInsufficientMirrorsUsed) return true;
+    return isNeededForReflection(element);
+  }
+
   bool isNeededForReflection(Element element) {
     if (hasInsufficientMirrorsUsed) return isTreeShakingDisabled;
     /// Record the name of [element] in [symbolsUsed]. Return true for