Add HCreateBox

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

Index: pkg/compiler/lib/src/ssa/codegen.dart
diff --git a/pkg/compiler/lib/src/ssa/codegen.dart b/pkg/compiler/lib/src/ssa/codegen.dart
index 4b8693cbf986f02c762763c4cd3026a7b5a6b646..20163ce776ddf4b2ee8320a8a635b45398187239 100644
--- a/pkg/compiler/lib/src/ssa/codegen.dart
+++ b/pkg/compiler/lib/src/ssa/codegen.dart
@@ -2109,6 +2109,10 @@ class SsaCodeGenerator implements HVisitor, HBlockInformationVisitor {
     }
   }
 
+  visitCreateBox(HCreateBox node) {
+    push(new js.ObjectInitializer(<js.Property>[]));
+  }
+
   js.Expression newLiteralBool(
       bool value, SourceInformation sourceInformation) {
     if (_options.enableMinification) {