Implement type inference for conventional for-loops.

pkg/front_end/lib/src/fasta/type_inference/type_inference_listener.dart

 // Copyright (c) 2017, 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.md file.
 
 import 'package:front_end/src/fasta/type_inference/type_inference_engine.dart';
 import 'package:kernel/ast.dart';
 
 /// Base class for [TypeInferenceListener] that defines the API for debugging.
 ///
 /// By default no debug info is printed.  To enable debug printing, mix in
@@ skipping 131 matching lines @@
 
   void expressionStatementExit(ExpressionStatement statement) =>
       debugStatementExit('expressionStatement', statement);
 
   void forInStatementEnter(ForInStatement statement) =>
       debugStatementEnter('forInStatement', statement);
 
   void forInStatementExit(ForInStatement statement) =>
       debugStatementExit('forInStatement', statement);
 
+  void forStatementEnter(ForStatement statement) =>
+      debugStatementEnter('forStatement', statement);
+
+  void forStatementExit(ForStatement statement) =>
+      debugStatementExit('forStatement', statement);
+
   void functionDeclarationEnter(FunctionDeclaration statement) =>
       debugStatementEnter('functionDeclaration', statement);
 
   void functionDeclarationExit(FunctionDeclaration statement) =>
       debugStatementExit('functionDeclaration', statement);
 
   bool functionExpressionEnter(
           FunctionExpression expression, DartType typeContext) =>
       debugExpressionEnter("functionExpression", expression, typeContext);
 
@@ skipping 157 matching lines @@
 
   void variableSetExit(VariableSet expression, DartType inferredType) =>
       debugExpressionExit("variableSet", expression, inferredType);
 
   void yieldStatementEnter(YieldStatement statement) =>
       debugStatementEnter('yieldStatement', statement);
 
   void yieldStatementExit(YieldStatement statement) =>
       debugStatementExit('yieldStatement', statement);
 }