All strong mode cleaning of dart2js.

tests/compiler/dart2js/simple_inferrer_const_closure_default_test.dart

Index: tests/compiler/dart2js/simple_inferrer_const_closure_default_test.dart
diff --git a/tests/compiler/dart2js/simple_inferrer_const_closure_default_test.dart b/tests/compiler/dart2js/simple_inferrer_const_closure_default_test.dart
index ce1cc2cc09ffc6dfe172fcc2bf35ec9f7979a7a9..cd1f33dc35c43d4f41373c8766a9606a0b2f3c28 100644
--- a/tests/compiler/dart2js/simple_inferrer_const_closure_default_test.dart
+++ b/tests/compiler/dart2js/simple_inferrer_const_closure_default_test.dart
@@ -46,7 +46,7 @@ void main() {
         var closedWorld = typesInferrer.closedWorld;
 
         checkArgument(String functionName, type) {
-          var functionElement = findElement(compiler, functionName);
+          dynamic functionElement = findElement(compiler, functionName);
           var signature = functionElement.functionSignature;
           var element = signature.requiredParameterCount > 0
               ? signature.requiredParameters.first
@@ -57,16 +57,6 @@ void main() {
               functionName);
         }
 
-        checkOptionalArgument(String functionName, type) {
-          var functionElement = findElement(compiler, functionName);
-          var signature = functionElement.functionSignature;
-          var element = signature.optionalParameters.first;
-          Expect.equals(
-              type,
-              simplify(typesInferrer.getTypeOfElement(element), closedWorld),
-              functionName);
-        }
-
         checkArgument('foo1', closedWorld.commonMasks.functionType);
 
         /// 01: ok