Make some parser test helper methods non-static.

pkg/analyzer/test/dart/ast/visitor_test.dart

Index: pkg/analyzer/test/dart/ast/visitor_test.dart
diff --git a/pkg/analyzer/test/dart/ast/visitor_test.dart b/pkg/analyzer/test/dart/ast/visitor_test.dart
index 5c7d14f4a381700aa3e0ae681218fbdd4b6486e0..0753c108521b9a9227232c0ea3177b1bb55b8d13 100644
--- a/pkg/analyzer/test/dart/ast/visitor_test.dart
+++ b/pkg/analyzer/test/dart/ast/visitor_test.dart
@@ -40,7 +40,7 @@ A f(var p) {
     return null;
   }
 }''';
-    CompilationUnit unit = ParserTestCase.parseCompilationUnit(source);
+    CompilationUnit unit = parseCompilationUnit(source);
     List<AstNode> nodes = new List<AstNode>();
     BreadthFirstVisitor<Object> visitor =
         new _BreadthFirstVisitorTestHelper(nodes);