Address long-standing review comments.

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 754 matching lines @@
     void ensure(ClassElement classElement) {
       if (classElement != null) {
         enqueuer.registerInstantiatedClass(classElement, elements);
       }
     }
     enqueueInResolution(getExceptionUnwrapper(), elements);
     ensure(jsPlainJavaScriptObjectClass);
     ensure(jsUnknownJavaScriptObjectClass);
   }
 
-  void registerWrapException(TreeElements elements) {
+  void registerThrowExpression(TreeElements elements) {
+    // We don't know ahead of time whether we will need the throw in a
+    // statement context or an expression context, so we register both
+    // here, even though we may not need the throwExpression helper.
     enqueueInResolution(getWrapExceptionHelper(), elements);
-  }
-
-  void registerThrowExpression(TreeElements elements) {
     enqueueInResolution(getThrowExpressionHelper(), elements);
   }
 
   void registerLazyField(TreeElements elements) {
     enqueueInResolution(getCyclicThrowHelper(), elements);
   }
 
   void registerTypeLiteral(Element element, TreeElements elements) {
     enqueueInResolution(getCreateRuntimeType(), elements);
     // TODO(ahe): Might want to register [element] as an instantiated class
@@ skipping 804 matching lines @@
     copy(constant.values);
     copy(constant.protoValue);
     copy(constant);
   }
 
   void visitConstructed(ConstructedConstant constant) {
     copy(constant.fields);
     copy(constant);
   }
 }