dart2js cps: Fix return type for native functions.

pkg/compiler/lib/src/cps_ir/cps_ir_builder.dart

 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 library dart2js.ir_builder;
 
 import '../closure.dart' as closure;
 import '../common.dart';
 import '../common/names.dart' show
     Names,
@@ skipping 2044 matching lines @@
       code = "$code = ${argumentTemplates.single}";
     } else {
       assert(argumentTemplates.isEmpty);
       assert(function.kind == ElementKind.GETTER);
     }
     // Generate the [ForeignCode] expression and a return statement to return
     // its value.
     ir.Primitive value = buildForeignCode(
         js.js.uncachedExpressionTemplate(code),
         arguments,
-        behavior);
+        behavior,
+        type: program.getTypeMaskForNativeFunction(function));
     buildReturn(value: value, sourceInformation: source);
   }
 
   /// Create a blocks of [statements] by applying [build] to all reachable
   /// statements. The first statement is assumed to be reachable.
   // TODO(johnniwinther): Type [statements] as `Iterable` when `NodeList` uses
   // `List` instead of `Link`.
   void buildBlock(var statements, BuildFunction build) {
     // Build(Block(stamements), C) = C'
     //   where C' = statements.fold(Build, C)
@@ skipping 551 matching lines @@
   }
 
   ir.Primitive buildInvocationMirror(Selector selector,
                                      List<ir.Primitive> arguments) {
     return addPrimitive(new ir.CreateInvocationMirror(selector, arguments));
   }
 
   ir.Primitive buildForeignCode(js.Template codeTemplate,
                                 List<ir.Primitive> arguments,
                                 NativeBehavior behavior,
-                                {Element dependency}) {
+                                {Element dependency,
+                                 TypeMask type}) {
     assert(behavior != null);
-    TypeMask type = program.getTypeMaskForForeign(behavior);
+    if (type == null) {
+      type = program.getTypeMaskForForeign(behavior);
+    }
     ir.Primitive result = addPrimitive(new ir.ForeignCode(
         codeTemplate,
         type,
         arguments,
         behavior,
         dependency: dependency));
     if (!codeTemplate.isExpression) {
       // Close the term if this is a "throw" expression or native body.
       add(new ir.Unreachable());
       _current = null;
@@ skipping 184 matching lines @@
 }
 
 class SwitchCaseInfo {
   final List<ir.Primitive> constants = <ir.Primitive>[];
   final SubbuildFunction buildBody;
 
   SwitchCaseInfo(this.buildBody);
 
   void addConstant(ir.Primitive constant) => constants.add(constant);
 }