Take inheritance into account when computing the elements accessible by mirrors.

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

Index: sdk/lib/_internal/compiler/implementation/deferred_load.dart
diff --git a/sdk/lib/_internal/compiler/implementation/deferred_load.dart b/sdk/lib/_internal/compiler/implementation/deferred_load.dart
index 5a0335d9c8379d9a3b893e543af208f75b30c71e..bade22fbdf2d4bd37f6808c0154b60e1b85baa7f 100644
--- a/sdk/lib/_internal/compiler/implementation/deferred_load.dart
+++ b/sdk/lib/_internal/compiler/implementation/deferred_load.dart
@@ -471,7 +471,7 @@ class DeferredLoadTask extends CompilerTask {
       // asked isNeededForReflection. Instead an internal error is triggered.
       // So we have to filter them out here.
       if (element is AnalyzableElementX && !element.hasTreeElements) return;
-      if (compiler.backend.isNeededForReflection(element)) {
+      if (compiler.backend.isAccessibleByReflection(element)) {
         _mapDependencies(element, deferredImport, isMirrorUsage: true);
       }
     }