Implement the new '?.' operator in analyzer.

pkg/analyzer/test/generated/ast_test.dart

 // Copyright (c) 2014, 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.
 
 // This code was auto-generated, is not intended to be edited, and is subject to
 // significant change. Please see the README file for more information.
 
 library engine.ast_test;
 
 import 'package:analyzer/src/generated/ast.dart';
@@ skipping 2749 matching lines @@
 
   void test_visitMethodDeclaration_withMetadata() {
     MethodDeclaration declaration = AstFactory.methodDeclaration2(null, null,
         null, null, AstFactory.identifier3("m"),
         AstFactory.formalParameterList(), AstFactory.blockFunctionBody2());
     declaration.metadata
         .add(AstFactory.annotation(AstFactory.identifier3("deprecated")));
     _assertSource("@deprecated m() {}", declaration);
   }
 
+  void test_visitMethodInvocation_conditional() {
+    _assertSource("t?.m()", AstFactory.methodInvocation(
+        AstFactory.identifier3("t"), "m", null, TokenType.QUESTION_PERIOD));
+  }
+
   void test_visitMethodInvocation_noTarget() {
     _assertSource("m()", AstFactory.methodInvocation2("m"));
   }
 
   void test_visitMethodInvocation_target() {
     _assertSource(
         "t.m()", AstFactory.methodInvocation(AstFactory.identifier3("t"), "m"));
   }
 
   void test_visitNamedExpression() {
@@ skipping 452 matching lines @@
   static const List<WrapperKind> values = const [
     PREFIXED_LEFT,
     PREFIXED_RIGHT,
     PROPERTY_LEFT,
     PROPERTY_RIGHT,
     NONE
   ];
 
   const WrapperKind(String name, int ordinal) : super(name, ordinal);
 }