Fix runtime strong mode error in ListMixin

pkg/dev_compiler/lib/src/compiler/code_generator.dart

Index: pkg/dev_compiler/lib/src/compiler/code_generator.dart
diff --git a/pkg/dev_compiler/lib/src/compiler/code_generator.dart b/pkg/dev_compiler/lib/src/compiler/code_generator.dart
index f1c8f8a18b0bef109627198e288672561d769435..e622041f0cfb706bbedff7101b4c3c67295f347b 100644
--- a/pkg/dev_compiler/lib/src/compiler/code_generator.dart
+++ b/pkg/dev_compiler/lib/src/compiler/code_generator.dart
@@ -1315,7 +1315,7 @@ class CodeGenerator extends GeneralizingAstVisitor
       jsMethods.add(new JS.Method(
           _propertyName('constructor'),
           js.call('function(...args) { return this.new.apply(this, args); }')
-              as JS.Fun));
+          as JS.Fun));
     } else if (ctors.isEmpty) {
       jsMethods.add(_emitImplicitConstructor(node, fields, virtualFields));
     }
@@ -3968,7 +3968,7 @@ class CodeGenerator extends GeneralizingAstVisitor
           new JS.Method(
               access,
               js.call('function() { return #; }', _visitInitializer(node))
-                  as JS.Fun,
+              as JS.Fun,
               isGetter: true),
           node,
           _findAccessor(element, getter: true)));
@@ -4528,7 +4528,7 @@ class CodeGenerator extends GeneralizingAstVisitor
       }
       result = astFactory.prefixedIdentifier(
           _bindValue(scope, 'o', ident.prefix, context: context)
-              as SimpleIdentifier,
+          as SimpleIdentifier,
           ident.period,
           ident.identifier);
     } else {