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

pkg/analyzer/test/generated/engine_test.dart

Index: pkg/analyzer/test/generated/engine_test.dart
diff --git a/pkg/analyzer/test/generated/engine_test.dart b/pkg/analyzer/test/generated/engine_test.dart
index 1095cb6d5703baec2060b61324a46e7af6ef016b..f6e60396bb42e5bd8a514edf9d012c92279f5f9d 100644
--- a/pkg/analyzer/test/generated/engine_test.dart
+++ b/pkg/analyzer/test/generated/engine_test.dart
@@ -5798,6 +5798,11 @@ class TestAnalysisContext implements InternalAnalysisContext {
   }
 
   @override
+  bool shouldErrorsBeAnalyzed(Source source, Object entry) {
+    fail("Unexpected invocation of shouldErrorsBeAnalyzed");
+    return false;
+  }
+  @override
   void visitCacheItems(void callback(Source source, SourceEntry dartEntry,
       DataDescriptor rowDesc, CacheState state)) {
     fail("Unexpected invocation of visitCacheItems");