Make mappedBy lazy.

sdk/lib/_internal/compiler/implementation/ssa/codegen.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 ssa;
 
 class SsaCodeGeneratorTask extends CompilerTask {
 
   final JavaScriptBackend backend;
 
@@ skipping 1119 matching lines @@
   }
 
   void emitAssignment(String destination, String source) {
     assignVariable(destination, new js.VariableUse(source));
   }
 
   /**
    * Sequentialize a list of conceptually parallel copies. Parallel
    * copies may contain cycles, that this method breaks.
    */
-  void sequentializeCopies(List<Copy> copies,
+  void sequentializeCopies(Iterable<Copy> copies,
                            String tempName,
                            void doAssignment(String target, String source)) {
     // Map to keep track of the current location (ie the variable that
     // holds the initial value) of a variable.
     Map<String, String> currentLocation = new Map<String, String>();
 
     // Map to keep track of the initial value of a variable.
     Map<String, String> initialValue = new Map<String, String>();
 
     // List of variables to assign a value.
@@ skipping 62 matching lines @@
         ready.add(current);
       }
     }
   }
 
   void assignPhisOfSuccessors(HBasicBlock node) {
     CopyHandler handler = variableNames.getCopyHandler(node);
     if (handler == null) return;
 
     // Map the instructions to strings.
-    List<Copy> copies = handler.copies.mappedBy((Copy copy) {
+    Iterable<Copy> copies = handler.copies.mappedBy((Copy copy) {
       return new Copy(variableNames.getName(copy.source),
                       variableNames.getName(copy.destination));
     });
 
     sequentializeCopies(copies, variableNames.getSwapTemp(), emitAssignment);
 
     for (Copy copy in handler.assignments) {
       String name = variableNames.getName(copy.destination);
       use(copy.source);
       assignVariable(name, pop());
@@ skipping 1867 matching lines @@
   if (leftType.canBeNull() && rightType.canBeNull()) {
     if (left.isConstantNull() || right.isConstantNull() ||
         (leftType.isPrimitive() && leftType == rightType)) {
       return '==';
     }
     return null;
   } else {
     return '===';
   }
 }