dart2js: Implement frequency based naming.

pkg/compiler/lib/src/dart2js.dart

Index: pkg/compiler/lib/src/dart2js.dart
diff --git a/pkg/compiler/lib/src/dart2js.dart b/pkg/compiler/lib/src/dart2js.dart
index 9db2af57cf29119b7fbd38b927137eb6456363a9..09b9880c5474c775c76cf94bd148d703461087b0 100644
--- a/pkg/compiler/lib/src/dart2js.dart
+++ b/pkg/compiler/lib/src/dart2js.dart
@@ -311,6 +311,7 @@ Future<api.CompilationResult> compile(List<String> argv) {
         '--output-type=dart|--output-type=dart-multi|--output-type=js',
         setOutputType),
     new OptionHandler('--use-cps-ir', passThrough),
+    new OptionHandler('--use-frequency-naming', passThrough),
     new OptionHandler('--verbose', setVerbose),
     new OptionHandler('--version', (_) => wantVersion = true),
     new OptionHandler('--library-root=.+', setLibraryRoot),
@@ -648,6 +649,9 @@ be removed in a future version:
 
   --use-cps-ir
     Experimental.  Use the new CPS based backend for code generation.
+
+  --use-frequency-naming
+    Experimental.  Use the new frequency based minifying namer.
 '''.trim());
 }