Reapply "Rename mappedBy to map."

sdk/lib/_internal/compiler/implementation/dart_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 dart_backend;
 
 // TODO(ahe): This class is simply wrong.  This backend should use
 // elements when it can, not AST nodes.  Perhaps a [Map<Element,
 // TreeElements>] is what is needed.
 class ElementAst {
@@ skipping 119 matching lines @@
    * 2) The code has typedefs in right hand side of IS checks,
    * 3) The code has classes which extend typedefs, have type arguments typedefs
    *    or type variable bounds typedefs.
    * These restrictions can be less strict.
    */
   bool isSafeToRemoveTypeDeclarations(
       Map<ClassElement, Set<Element>> classMembers) {
     Set<DartType> processedTypes = new Set<DartType>();
     List<DartType> workQueue = new List<DartType>();
     workQueue.addAll(
-        classMembers.keys.mappedBy((classElement) => classElement.thisType));
+        classMembers.keys.map((classElement) => classElement.thisType));
     workQueue.addAll(compiler.resolverWorld.isChecks);
     Element typeErrorElement =
         compiler.coreLibrary.find(new SourceString('TypeError'));
     DartType typeErrorType = typeErrorElement.computeType(compiler);
     if (workQueue.indexOf(typeErrorType) != -1) {
       return false;
     }
 
     void processTypeArguments(Element classElement, NodeList typeArguments) {
       if (typeArguments == null) return;
@@ skipping 433 matching lines @@
 }
 
 compareElements(e0, e1) {
   int result = compareBy((e) => e.getLibrary().canonicalUri.toString())(e0, e1);
   if (result != 0) return result;
   return compareBy((e) => e.position().charOffset)(e0, e1);
 }
 
 List<Element> sortElements(Iterable<Element> elements) =>
     sorted(elements, compareElements);