Use entities in native_emitter.dart

pkg/compiler/lib/src/native/ssa.dart

Index: pkg/compiler/lib/src/native/ssa.dart
diff --git a/pkg/compiler/lib/src/native/ssa.dart b/pkg/compiler/lib/src/native/ssa.dart
index e0839a0dca1888e7bec3027202e0e5680e0127e2..20d1ee311153192ae3cdc7f67cad5fe460f3f2e0 100644
--- a/pkg/compiler/lib/src/native/ssa.dart
+++ b/pkg/compiler/lib/src/native/ssa.dart
@@ -28,7 +28,7 @@ void handleSsaNative(SsaBuilder builder, Expression nativeBody) {
       ParameterElement parameter, ResolutionFunctionType type) {
     HInstruction local = builder.localsHandler.readLocal(parameter);
     ConstantValue arityConstant =
-        builder.constantSystem.createInt(type.computeArity());
+        builder.constantSystem.createInt(type.parameterTypes.length);
     HInstruction arity =
         builder.graph.addConstant(arityConstant, builder.closedWorld);
     // TODO(ngeoffray): For static methods, we could pass a method with a