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

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

 // Copyright (c) 2015, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 part of dart2js.js_emitter.startup_emitter.model_emitter;
 
 /// The name of the property that stores the tear-off getter on a static
 /// function.
 ///
 /// This property is only used when isolates are used.
@@ skipping 500 matching lines @@
      'lazyStatics': emitLazilyInitializedStatics(fragment),
      'types': deferredTypes,
      // TODO(floitsch): only call emitNativeSupport if we need native.
      'nativeSupport': emitNativeSupport(fragment),
     });
   }
 
   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.
   ///
   /// The emitted holders contain classes (only the constructors) and all
   /// static functions.
   js.Statement emitHolders(List<Holder> holders, Fragment fragment) {
     // Skip the static-state holder in this function.
     holders = holders
         .where((Holder holder) => !holder.isStaticStateHolder)
@@ skipping 763 matching lines @@
     }
     statements.add(js.js.statement("setOrUpdateInterceptorsByTag(#);",
         js.objectLiteral(interceptorsByTag)));
     statements.add(js.js.statement("setOrUpdateLeafTags(#);",
         js.objectLiteral(leafTags)));
     statements.add(subclassAssignment);
 
     return new js.Block(statements);
   }
 }