dart2js: Use an abstract Name class for names in the generated JavaScript ast.

pkg/compiler/lib/src/js_emitter/native_emitter.dart

 // Copyright (c) 2012, 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;
 
 class NativeEmitter {
 
   final Map<Element, ClassBuilder> cachedBuilders;
 
@@ skipping 176 matching lines @@
 
         List<Class> extensions = extensionPoints[cls];
 
         String leafStr = formatTags(leafTags[cls]);
         String nonleafStr = formatTags(nonleafTags[cls]);
 
         StringBuffer sb = new StringBuffer(leafStr);
         if (nonleafStr != '') {
           sb..write(';')..write(nonleafStr);
         }
-        if (extensions != null) {
-          sb..write(';')
-            ..writeAll(extensions.map((Class cls) => cls.name), '|');
-        }
+
         String encoding = sb.toString();
 
-        if (cls.isNative || encoding != '') {
+        if (cls.isNative || encoding != '' || extensions != null) {
+          List<jsAst.Literal> parts = <jsAst.Literal>[js.stringPart(encoding)];
+          if (extensions != null) {
+            parts..add(js.stringPart(';'))
+                 ..addAll(
+                     js.joinLiterals(extensions.map((Class cls) => cls.name),
+                                     js.stringPart('|')));
+          }
           assert(cls.nativeInfo == null);
-          cls.nativeInfo = encoding;
+          cls.nativeInfo = js.concatenateStrings(parts, addQuotes: true);
         }
       }
       generateClassInfo(jsInterceptorClass);
       for (Class cls in classes) {
         if (!cls.isNative || neededClasses.contains(cls)) {
           generateClassInfo(cls);
         }
       }
     }
 
@@ skipping 78 matching lines @@
             break;
           }
         }
       }
     });
   }
 
   List<jsAst.Statement> generateParameterStubStatements(
       FunctionElement member,
       bool isInterceptedMethod,
-      String invocationName,
+      jsAst.Name invocationName,
       List<jsAst.Parameter> stubParameters,
       List<jsAst.Expression> argumentsBuffer,
       int indexOfLastOptionalArgumentInParameters) {
     // The target JS function may check arguments.length so we need to
     // make sure not to pass any unspecified optional arguments to it.
     // For example, for the following Dart method:
     //   foo([x, y, z]);
     // The call:
     //   foo(y: 1)
     // must be turned into a JS call to:
@@ skipping 134 matching lines @@
           }
     ''', {'info': infoAccess,
           'constructor': constructorAccess,
           'subclassRead': subclassRead,
           'interceptorsByTagAccess': interceptorsByTagAccess,
           'leafTagsAccess': leafTagsAccess,
           'nativeSuperclassTagName': embeddedNames.NATIVE_SUPERCLASS_TAG_NAME,
           'allowNativesSubclassing': true});
   }
 }