If the element or selector is a setter, make sure to use the runtime setter name to know whether we…

sdk/lib/_internal/compiler/implementation/js_backend/backend.dart

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // 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.
 
 part of js_backend;
 
 class JavaScriptItemCompilationContext extends ItemCompilationContext {
   final Set<HInstruction> boundsChecked;
 
   JavaScriptItemCompilationContext()
@@ skipping 1559 matching lines @@
     } else if (element == preserveNamesMarker) {
       mustPreserveNames = true;
     } else if (element == preserveMetadataMarker) {
       mustRetainMetadata = true;
     }
   }
 
   /// Called when [:const Symbol(name):] is seen.
   void registerConstSymbol(String name, TreeElements elements) {
     symbolsUsed.add(name);
+    if (name.endsWith('=')) {
+      symbolsUsed.add(name.substring(0, name.length - 1));
+    }
   }
 
   /// Called when [:new Symbol(...):] is seen.
   void registerNewSymbol(TreeElements elements) {
   }
 
   /// Called when resolving the `Symbol` constructor.
   void registerSymbolConstructor(TreeElements elements) {
     // Make sure that collection_dev.Symbol.validated is registered.
     assert(compiler.symbolValidatedConstructor != null);
@@ skipping 249 matching lines @@
     copy(constant.values);
     copy(constant.protoValue);
     copy(constant);
   }
 
   void visitConstructed(ConstructedConstant constant) {
     copy(constant.fields);
     copy(constant);
   }
 }