Revert "Adjusts dart2js backend to handle method type arguments."

pkg/compiler/lib/src/compile_time_constants.dart

Index: pkg/compiler/lib/src/compile_time_constants.dart
diff --git a/pkg/compiler/lib/src/compile_time_constants.dart b/pkg/compiler/lib/src/compile_time_constants.dart
index c2d39d4e9ba59dca9a28a7bcaf3194c3f41c3b89..9a52c3ec1154f6b0ca83ba5f8ddbca372869ec7c 100644
--- a/pkg/compiler/lib/src/compile_time_constants.dart
+++ b/pkg/compiler/lib/src/compile_time_constants.dart
@@ -246,17 +246,9 @@ abstract class ConstantCompilerBase implements ConstantCompiler {
         ConstantValue value = getConstantValue(expression);
         if (elementType.isMalformed && !value.isNull) {
           if (isConst) {
-            // TODO(johnniwinther): Check that it is possible to reach this
-            // point in a situation where `elementType is! MalformedType`.
-            if (elementType is MalformedType) {
-              ErroneousElement element = elementType.element;
-              reporter.reportErrorMessage(
-                  node, element.messageKind, element.messageArguments);
-            } else {
-              assert(elementType is MethodTypeVariableType);
-              reporter.reportErrorMessage(
-                  node, MessageKind.TYPE_VARIABLE_FROM_METHOD_NOT_REIFIED);
-            }
+            ErroneousElement element = elementType.element;
+            reporter.reportErrorMessage(
+                node, element.messageKind, element.messageArguments);
           } else {
             // We need to throw an exception at runtime.
             expression = null;