Revert "Do not use the namer for naming closure elements."

pkg/compiler/lib/src/js_backend/minify_namer.dart

Index: pkg/compiler/lib/src/js_backend/minify_namer.dart
diff --git a/pkg/compiler/lib/src/js_backend/minify_namer.dart b/pkg/compiler/lib/src/js_backend/minify_namer.dart
index 45a10eb2d81059c9f5ef5f55106848b2165c0622..579429e82259688f042e27cd3e17a3d79707d9be 100644
--- a/pkg/compiler/lib/src/js_backend/minify_namer.dart
+++ b/pkg/compiler/lib/src/js_backend/minify_namer.dart
@@ -48,6 +48,15 @@ class MinifyNamer extends Namer {
     return freshName;
   }
 
+  String getClosureVariableName(String _, int id) {
+    if (id < ALPHABET_CHARACTERS) {
+      return new String.fromCharCodes([_letterNumber(id)]);
+    }
+    // Fall back to a slightly longer name.
+    String basename = _disambiguateMember(null, 'closure');
+    return '${basename}_$id';
+  }
+
   // From issue 7554.  These should not be used on objects (as instance
   // variables) because they clash with names from the DOM. However, it is
   // OK to use them as fields, as we only access fields directly if we know