emit interfaces before use

test/codegen/expect/sunflower/dom.js

Index: test/codegen/expect/sunflower/dom.js
diff --git a/test/codegen/expect/sunflower/dom.js b/test/codegen/expect/sunflower/dom.js
index 62d83cdbe91307e23f5b0fc36916cbd4c605fbcd..87855b83335f3b4e02f8afd15880ee5ae47474e3 100644
--- a/test/codegen/expect/sunflower/dom.js
+++ b/test/codegen/expect/sunflower/dom.js
@@ -12,10 +12,8 @@ var dom;
     }
   }
   let overload = new Overload();
-  class Event extends core.Object {
-  }
-  class RenderingContext extends core.Object {
-  }
+  class Event extends core.Object {}
+  class RenderingContext extends core.Object {}
   class CanvasDrawingStyles extends core.Object {
     CanvasDrawingStyles() {
       this.lineWidth = null;
@@ -28,8 +26,7 @@ var dom;
       this.textBaseline = null;
     }
   }
-  class CanvasPathMethods extends core.Object {
-  }
+  class CanvasPathMethods extends core.Object {}
   // Exports:
   exports.JsName = JsName;
   exports.Overload = Overload;