dart2dart: Restore loops with conditions and updates in backend.

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 219 matching lines @@
       } else {
         ir.FunctionDefinition function = compiler.irBuilder.getIr(element);
         tree.Builder builder = new tree.Builder(compiler);
         tree.FunctionDefinition definition = builder.build(function);
         assert(definition != null);
         compiler.tracer.traceCompilation(element.name, null, compiler);
         compiler.tracer.traceGraph('Tree builder', definition);
         treeElements = new TreeElementMapping(element);
         new tree.StatementRewriter().rewrite(definition);
         compiler.tracer.traceGraph('Statement rewriter', definition);
+        new tree.LoopRewriter().rewrite(definition);
+        compiler.tracer.traceGraph('Loop rewriter', definition);
         new tree.LogicalRewriter().rewrite(definition);
         compiler.tracer.traceGraph('Logical rewriter', definition);
         node = dart_codegen.emit(element, treeElements, definition);
       }
       return new ElementAst(node, treeElements);
     }
 
     Set<Element> topLevelElements = new Set<Element>();
     Map<ClassElement, Set<Element>> classMembers =
         new Map<ClassElement, Set<Element>>();
@@ skipping 384 matching lines @@
   }
 
   Constant compileMetadata(MetadataAnnotation metadata,
                            Node node,
                            TreeElements elements) {
     return measure(() {
       return constantCompiler.compileMetadata(metadata, node, elements);
     });
   }
 }