Use MODIFICATION_TIME in ScanDartTask and ParseHtmlTask.

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

Index: pkg/analyzer/test/src/task/html_test.dart
diff --git a/pkg/analyzer/test/src/task/html_test.dart b/pkg/analyzer/test/src/task/html_test.dart
index c8f1f9778b775f9be0184d019fa6ef8172b15c8b..a41cc1c797a4d761641ea32868aa6499496d979e 100644
--- a/pkg/analyzer/test/src/task/html_test.dart
+++ b/pkg/analyzer/test/src/task/html_test.dart
@@ -265,7 +265,12 @@ class ParseHtmlTaskTest extends AbstractContextTest {
     Source source = newSource('/test.html');
     Map<String, TaskInput> inputs = ParseHtmlTask.buildInputs(source);
     expect(inputs, isNotNull);
-    expect(inputs.keys, unorderedEquals([ParseHtmlTask.CONTENT_INPUT_NAME]));
+    expect(
+        inputs.keys,
+        unorderedEquals([
+          ParseHtmlTask.CONTENT_INPUT_NAME,
+          ParseHtmlTask.MODIFICATION_TIME_INPUT
+        ]));
   }
 
   test_constructor() {