Remove ConstantExpression.value

pkg/compiler/lib/src/js_emitter/parameter_stub_generator.dart

Index: pkg/compiler/lib/src/js_emitter/parameter_stub_generator.dart
diff --git a/pkg/compiler/lib/src/js_emitter/parameter_stub_generator.dart b/pkg/compiler/lib/src/js_emitter/parameter_stub_generator.dart
index 7d5122ba4acbb047720a26c9a85d9e6aed2f67d5..2e9ed2176bff4f0f7769ce828e0fe93f3f5c7693 100644
--- a/pkg/compiler/lib/src/js_emitter/parameter_stub_generator.dart
+++ b/pkg/compiler/lib/src/js_emitter/parameter_stub_generator.dart
@@ -100,12 +100,11 @@ class ParameterStubGenerator {
           parametersBuffer[optionalParameterStart + index] =
               new jsAst.Parameter(jsName);
         } else {
-          ConstantExpression constant = handler.getConstantForVariable(element);
-          if (constant == null) {
+          ConstantValue value = handler.getConstantValueForVariable(element);
+          if (value == null) {
             argumentsBuffer[count] =
                 emitter.constantReference(new NullConstantValue());
           } else {
-            ConstantValue value = constant.value;
             if (!value.isNull) {
               // If the value is the null constant, we should not pass it
               // down to the native method.