Scanner/parser support for DEP 9 (null-aware operators).

pkg/analyzer/test/generated/ast_test.dart

Index: pkg/analyzer/test/generated/ast_test.dart
diff --git a/pkg/analyzer/test/generated/ast_test.dart b/pkg/analyzer/test/generated/ast_test.dart
index 535c75b68eef4e64a30ae948d8329ceee330e474..42137e263a45c138a65ce5c6af36d7b3bc046987 100644
--- a/pkg/analyzer/test/generated/ast_test.dart
+++ b/pkg/analyzer/test/generated/ast_test.dart
@@ -2848,6 +2848,11 @@ class ToSourceVisitorTest extends EngineTestCase {
         "a.b", AstFactory.propertyAccess2(AstFactory.identifier3("a"), "b"));
   }
 
+  void test_visitPropertyAccess_conditional() {
+    _assertSource("a?.b", AstFactory.propertyAccess2(
+        AstFactory.identifier3("a"), "b", TokenType.QUESTION_PERIOD));
+  }
+
   void test_visitRedirectingConstructorInvocation_named() {
     _assertSource(
         "this.c()", AstFactory.redirectingConstructorInvocation2("c"));