Remove requiredTypes

pkg/compiler/lib/src/typechecker.dart

Index: pkg/compiler/lib/src/typechecker.dart
diff --git a/pkg/compiler/lib/src/typechecker.dart b/pkg/compiler/lib/src/typechecker.dart
index a21913aac27db74fb86e7af9f50291621a88969f..45cd0810149ebff3bcf2ae44654c0eeb234a20eb 100644
--- a/pkg/compiler/lib/src/typechecker.dart
+++ b/pkg/compiler/lib/src/typechecker.dart
@@ -1590,7 +1590,7 @@ class TypeCheckerVisitor extends Visitor<DartType> {
   }
 
   DartType visitLiteralSymbol(LiteralSymbol node) {
-    return compiler.symbolClass.rawType;
+    return coreTypes.symbolType;
   }
 
   DartType computeConstructorType(ConstructorElement constructor,
@@ -1829,8 +1829,6 @@ class TypeCheckerVisitor extends Visitor<DartType> {
   visitAsyncForIn(AsyncForIn node) {
     DartType elementType = computeForInElementType(node);
     DartType expressionType = analyze(node.expression);
-    // TODO(johnniwinther): Move this to _CompilerCoreTypes.
-    compiler.streamClass.ensureResolved(resolution);
     DartType streamOfDynamic = coreTypes.streamType();
     if (!types.isAssignable(expressionType, streamOfDynamic)) {
       reportMessage(node.expression,