Record SourceKind.UNKNOWN for not existing sources.

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

Index: pkg/analyzer/test/src/task/dart_test.dart
diff --git a/pkg/analyzer/test/src/task/dart_test.dart b/pkg/analyzer/test/src/task/dart_test.dart
index c1dff794247c50c6bdd96b3f61bca1ceef39cdd9..0e236efe4cd3f75de13cf4bf196683828bc07b58 100644
--- a/pkg/analyzer/test/src/task/dart_test.dart
+++ b/pkg/analyzer/test/src/task/dart_test.dart
@@ -2093,6 +2093,7 @@ class ParseDartTaskTest extends _AbstractDartTaskTest {
     expect(inputs, isNotNull);
     expect(inputs.keys, unorderedEquals([
       ParseDartTask.LINE_INFO_INPUT_NAME,
+      ParseDartTask.MODIFICATION_TIME_INPUT_NAME,
       ParseDartTask.TOKEN_STREAM_INPUT_NAME
     ]));
   }
@@ -2136,6 +2137,19 @@ class B {}''');
     expect(outputs[UNITS], hasLength(1));
   }
 
+  test_perform_doesNotExist() {
+    _performParseTask(null);
+    expect(outputs, hasLength(8));
+    expect(outputs[EXPLICITLY_IMPORTED_LIBRARIES], hasLength(0));
+    expect(outputs[EXPORTED_LIBRARIES], hasLength(0));
+    _assertHasCore(outputs[IMPORTED_LIBRARIES], 1);
+    expect(outputs[INCLUDED_PARTS], hasLength(0));
+    expect(outputs[PARSE_ERRORS], hasLength(0));
+    expect(outputs[PARSED_UNIT], isNotNull);
+    expect(outputs[SOURCE_KIND], SourceKind.UNKNOWN);
+    expect(outputs[UNITS], hasLength(1));
+  }
+
   test_perform_invalidDirectives() {
     _performParseTask(r'''
 library lib;