Remove code supporting incremental compilation in dart2js

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

Index: pkg/compiler/lib/src/js_backend/namer.dart
diff --git a/pkg/compiler/lib/src/js_backend/namer.dart b/pkg/compiler/lib/src/js_backend/namer.dart
index ffb780033734ba0cf397ee0142143014fa24eb44..0f0e80d3abdc450cb7b111c10d45617aae784854 100644
--- a/pkg/compiler/lib/src/js_backend/namer.dart
+++ b/pkg/compiler/lib/src/js_backend/namer.dart
@@ -1711,18 +1711,6 @@ class Namer {
       return name;
     }
   }
-
-  String get incrementalHelperName => r'$dart_unsafe_incremental_support';
-
-  jsAst.Expression get accessIncrementalHelper {
-    return js('self.${incrementalHelperName}');
-  }
-
-  void forgetElement(Element element) {
-    jsAst.Name globalName = userGlobals[element];
-    invariant(element, globalName != null, message: 'No global name.');
-    userGlobals.remove(element);
-  }
 }
 
 /**