Separate Dart backend specific logic from basic Unparser.

lib/compiler/implementation/dart_backend/emitter.dart

Index: lib/compiler/implementation/dart_backend/emitter.dart
diff --git a/lib/compiler/implementation/dart_backend/emitter.dart b/lib/compiler/implementation/dart_backend/emitter.dart
index 5b16c27475d5de8d44117cbefa91277823b139c0..a19d34546e5cb1beaa8f7946cd16caf2d572650a 100644
--- a/lib/compiler/implementation/dart_backend/emitter.dart
+++ b/lib/compiler/implementation/dart_backend/emitter.dart
@@ -2,13 +2,36 @@
 // 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.
 
+class EmitterUnparser extends Unparser {
+  final Map<Node, String> renames;
+
+  EmitterUnparser(this.renames);
+
+  visit(Node node) {
+    if (node !== null && renames.containsKey(node)) {
+      sb.add(renames[node]);
+    } else {
+      super.visit(node);
+    }
+  }
+
+  unparseSendReceiver(Send node, [bool spacesNeeded=false]) {
+    // TODO(smok): Remove ugly hack for library preferences.

[Roman, 2012/10/01 14:10:34]

library prefixes?

+    // Check that renamer does not want to omit receiver at all,
+    // in that case we don't need spaces or dot.
+    if (node.receiver !== null && renames[node.receiver] == '') return;
+    super.unparseSendReceiver(node, spacesNeeded);
+  }
+}
+
 String emitCode(
       Compiler compiler,
-      Unparser unparser,
+      Map<Node, String> renames,
       Map<LibraryElement, String> imports,
       Collection<Element> topLevelElements,
       Map<ClassElement, Collection<Element>> classMembers) {
   final sb = new StringBuffer();
+  final unparser = new EmitterUnparser(renames);
   final processedVariableLists = new Set<VariableListElement>();
 
   void outputElement(Element element) {