DartWorkManager.getLibrariesContainingPart() should ask the ResultProvider for CONTAINING_LIBRARIES.

pkg/analyzer/test/src/task/dart_work_manager_test.dart

Index: pkg/analyzer/test/src/task/dart_work_manager_test.dart
diff --git a/pkg/analyzer/test/src/task/dart_work_manager_test.dart b/pkg/analyzer/test/src/task/dart_work_manager_test.dart
index 31ee542dea4f118a85f0aab6732416b633870fe5..65bf213a3b97aae9386115ec962aed412cc8fa37 100644
--- a/pkg/analyzer/test/src/task/dart_work_manager_test.dart
+++ b/pkg/analyzer/test/src/task/dart_work_manager_test.dart
@@ -329,6 +329,7 @@ class DartWorkManagerTest {
   }
 
   void test_getLibrariesContainingPart() {
+    when(context.aboutToComputeResult(anyObject, anyObject)).thenReturn(false);
     Source part1 = new TestSource('part1.dart');
     Source part2 = new TestSource('part2.dart');
     Source part3 = new TestSource('part3.dart');