Remove requiredTypes

pkg/compiler/lib/src/js_backend/backend_impact.dart

Index: pkg/compiler/lib/src/js_backend/backend_impact.dart
diff --git a/pkg/compiler/lib/src/js_backend/backend_impact.dart b/pkg/compiler/lib/src/js_backend/backend_impact.dart
index 90dba81a60a36c13749ea139a811677cca40f1d9..650645ed9ef2c1a0dfe9cf18d06a6947126c9bee 100644
--- a/pkg/compiler/lib/src/js_backend/backend_impact.dart
+++ b/pkg/compiler/lib/src/js_backend/backend_impact.dart
@@ -151,6 +151,11 @@ class BackendImpacts {
       staticUses: [
         helpers.compiler.symbolValidatedConstructor]);
 
+  BackendImpact get constSymbol => new BackendImpact(
+      instantiatedClasses: [
+        compiler.symbolClass],
+      staticUses: [
+        compiler.symbolConstructor.declaration]);
 
   BackendImpact get incDecOperation =>
       needsInt('Needed for the `+ 1` or `- 1` operation of ++/--.');
@@ -220,6 +225,8 @@ class BackendImpacts {
         helpers.createRuntimeType]);
 
   BackendImpact get stackTraceInCatch => new BackendImpact(
+      instantiatedClasses: [
+        helpers.compiler.stackTraceClass],
       staticUses: [
         helpers.traceFromException]);
 
@@ -286,4 +293,8 @@ class BackendImpacts {
         // JavaScript object prototype, so we make sure
         // [:defineProperty:] is compiled.
         helpers.defineProperty]);
+
+  BackendImpact get closure => new BackendImpact(
+      instantiatedClasses: [
+        helpers.compiler.functionClass]);
 }