Don't schedule LIBRARY_ERRORS_READY for libraries that should not be analyzed.

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 eb885df0aaad30ed3a82c00d84ba2b2c8d334583..3920def2f6f4b11dd7bff7d99911572e6b9ab164 100644
--- a/pkg/analyzer/test/src/task/dart_work_manager_test.dart
+++ b/pkg/analyzer/test/src/task/dart_work_manager_test.dart
@@ -506,6 +506,7 @@ class DartWorkManagerTest {
 
   void test_resultsComputed_sourceKind_isLibrary() {
     manager.unknownSourceQueue.addAll([source1, source2, source3]);
+    when(context.shouldErrorsBeAnalyzed(source2, null)).thenReturn(true);
     manager.resultsComputed(source2, {SOURCE_KIND: SourceKind.LIBRARY});
     expect_librarySourceQueue([source2]);
     expect_unknownSourceQueue([source1, source3]);