Fix tests under windows (TBR)

pkg/analyzer_plugin/test/src/utilities/completion/optype_test.dart

Index: pkg/analyzer_plugin/test/src/utilities/completion/optype_test.dart
diff --git a/pkg/analyzer_plugin/test/src/utilities/completion/optype_test.dart b/pkg/analyzer_plugin/test/src/utilities/completion/optype_test.dart
index c23ece8265a7ad4539f0e6f51d0c1459792b50a7..ddc6cc8f76ce429b719776034f0ce9df4f76e29c 100644
--- a/pkg/analyzer_plugin/test/src/utilities/completion/optype_test.dart
+++ b/pkg/analyzer_plugin/test/src/utilities/completion/optype_test.dart
@@ -21,7 +21,7 @@ main() {
 
 @reflectiveTest
 class OpTypeTest extends AbstractContextTest {
-  static const testpath = '/completionTest.dart';
+  String testpath;
   int completionOffset;
   OpType visitor;
 
@@ -73,6 +73,12 @@ class OpTypeTest extends AbstractContextTest {
     expect(visitor.suggestKind, kind, reason: 'suggestion kind');
   }
 
+  @override
+  void setUp() {
+    super.setUp();
+    testpath = provider.convertPath('/completionTest.dart');
+  }
+
   test_Annotation() async {
     // SimpleIdentifier  Annotation  MethodDeclaration  ClassDeclaration
     addTestSource('class C { @A^ }');