Typecheck const classes in the context of the constructor call.

pkg/compiler/lib/src/js_backend/constant_handler_javascript.dart

Index: pkg/compiler/lib/src/js_backend/constant_handler_javascript.dart
diff --git a/pkg/compiler/lib/src/js_backend/constant_handler_javascript.dart b/pkg/compiler/lib/src/js_backend/constant_handler_javascript.dart
index 008b709a179658883843f7942e7eae557fd57ab0..9bc3a86a016844cac6a1af67a8ce47a0c5c94fdb 100644
--- a/pkg/compiler/lib/src/js_backend/constant_handler_javascript.dart
+++ b/pkg/compiler/lib/src/js_backend/constant_handler_javascript.dart
@@ -44,6 +44,7 @@ class JavaScriptConstantTask extends ConstantCompilerTask {
   @override
   ConstantExpression compileConstant(VariableElement element) {
     return measure(() {
+      // TODO(het): Only report errors from one of the constant compilers
       ConstantExpression result = dartConstantCompiler.compileConstant(element);
       jsConstantCompiler.compileConstant(element);
       return result;
@@ -126,12 +127,13 @@ class JavaScriptConstantCompiler extends ConstantCompilerBase
 
   ConstantExpression compileVariableWithDefinitions(VariableElement element,
                                           TreeElements definitions,
-                                          {bool isConst: false}) {
+                                          {bool isConst: false,
+                                           bool checkType: true}) {
     if (!isConst && lazyStatics.contains(element)) {
       return null;
     }
     ConstantExpression value = super.compileVariableWithDefinitions(
-        element, definitions, isConst: isConst);
+        element, definitions, isConst: isConst, checkType: checkType);
     if (!isConst && value == null) {
       lazyStatics.add(element);
     }