dart2js: Add a header to the output of the startup emitter.

pkg/compiler/lib/src/js_emitter/startup_emitter/fragment_emitter.dart

Index: pkg/compiler/lib/src/js_emitter/startup_emitter/fragment_emitter.dart
diff --git a/pkg/compiler/lib/src/js_emitter/startup_emitter/fragment_emitter.dart b/pkg/compiler/lib/src/js_emitter/startup_emitter/fragment_emitter.dart
index f0b5a784f40891b31ef64e1680cfc755d14dee5f..c4e0012d3e9f053d5449b061bca48f4ec1a58f45 100644
--- a/pkg/compiler/lib/src/js_emitter/startup_emitter/fragment_emitter.dart
+++ b/pkg/compiler/lib/src/js_emitter/startup_emitter/fragment_emitter.dart
@@ -518,9 +518,10 @@ class FragmentEmitter {
   js.Statement emitDeferredInitializerGlobal(Map loadMap) {
     if (loadMap.isEmpty) return new js.Block.empty();
 
-    return js.js.statement("""
-    if (typeof(${ModelEmitter.deferredInitializersGlobal}) === 'undefined')
-      var ${ModelEmitter.deferredInitializersGlobal} = Object.create(null);""");
+    String global = ModelEmitter.deferredInitializersGlobal;
+    return js.js.statement(
+        "if (typeof($global) === 'undefined') var # = Object.create(null);",
+        new js.VariableDeclaration(global, allowRename: false));

[floitsch, 2015/08/04 15:06:38]

It worked before, but since this variable is shared between two different
fragments, I prefer to make it explicit that it must not be renamed.

   }
 
   /// Emits all holders, except for the static-state holder.