dart2js: Implement frequency based naming.

pkg/js_ast/lib/src/printer.dart

Index: pkg/js_ast/lib/src/printer.dart
diff --git a/pkg/js_ast/lib/src/printer.dart b/pkg/js_ast/lib/src/printer.dart
index ff757b4cbd90d87ec1863be0751e3c695f2e6ad4..94cec32f28548dafcc48ce024f3bd34d1be333ef 100644
--- a/pkg/js_ast/lib/src/printer.dart
+++ b/pkg/js_ast/lib/src/printer.dart
@@ -5,15 +5,21 @@
 part of js_ast;
 
 
+typedef String Renamer(Name);
+
 class JavaScriptPrintingOptions {
   final bool shouldCompressOutput;
   final bool minifyLocalVariables;
   final bool preferSemicolonToNewlineInMinifiedOutput;
+  final Renamer renamerForNames;
 
   JavaScriptPrintingOptions(
       {this.shouldCompressOutput: false,
        this.minifyLocalVariables: false,
-       this.preferSemicolonToNewlineInMinifiedOutput: false});
+       this.preferSemicolonToNewlineInMinifiedOutput: false,
+       this.renamerForNames: identityRenamer});
+
+  static String identityRenamer(Name name) => name.name;
 }
 
 
@@ -930,7 +936,7 @@ class Printer implements NodeVisitor {
     } else if (selector is Name) {
       if (access.receiver is LiteralNumber) out(" ", isWhitespace: true);
       out(".");
-      out(selector.name);
+      selector.accept(this);
       return;
     }
     out("[");
@@ -998,7 +1004,7 @@ class Printer implements NodeVisitor {
 
   @override
   visitName(Name node) {
-    out(node.name);
+    out(options.renamerForNames(node));
   }
 
   @override