Add support for parsing, but not capturing, assers in constructor initializer lists

pkg/analyzer/test/generated/parser_test.dart

Index: pkg/analyzer/test/generated/parser_test.dart
diff --git a/pkg/analyzer/test/generated/parser_test.dart b/pkg/analyzer/test/generated/parser_test.dart
index e48c4dca05c43a1a360aa3af00b602df058c92f9..72d36496457ea346ad1ff3db35f8e29311bc7453 100644
--- a/pkg/analyzer/test/generated/parser_test.dart
+++ b/pkg/analyzer/test/generated/parser_test.dart
@@ -7094,6 +7094,15 @@ void''');
 //        null, null, null, null, null, null}, "");
   }
 
+  void test_parseConstructor_assert() {
+    ClassMember classMember = parse("parseClassMember", <Object>["C"],
+        "C(x, y) : _x = x, assert (x < y), _y = y;");
+    expect(classMember, new isInstanceOf<ConstructorDeclaration>());
+    ConstructorDeclaration constructor = classMember as ConstructorDeclaration;
+    NodeList<ConstructorInitializer> initializers = constructor.initializers;
+    expect(initializers, hasLength(2));
+  }
+
   void test_parseConstructor_with_pseudo_function_literal() {
     // "(b) {}" should not be misinterpreted as a function literal even though
     // it looks like one.