Validate cache consistency asynchronously. Compute modification times of physical files in a separa…

pkg/analyzer/test/file_system/memory_file_system_test.dart

Index: pkg/analyzer/test/file_system/memory_file_system_test.dart
diff --git a/pkg/analyzer/test/file_system/memory_file_system_test.dart b/pkg/analyzer/test/file_system/memory_file_system_test.dart
index a6adddd21f97ca7bd4329d63b77db484eb07f870..2787ce2ca08736402270f17ca580a2c76e1305a7 100644
--- a/pkg/analyzer/test/file_system/memory_file_system_test.dart
+++ b/pkg/analyzer/test/file_system/memory_file_system_test.dart
@@ -615,6 +615,13 @@ class MemoryResourceProviderTest {
     }, throwsA(new isInstanceOf<ArgumentError>()));
   }
 
+  test_getModificationTimes() async {
+    File file = provider.newFile('/test.dart', '');
+    Source source = file.createSource();
+    List<int> times = await provider.getModificationTimes([source]);
+    expect(times, [source.modificationStamp]);
+  }
+
   test_watch_createFile() {
     String rootPath = '/my/path';
     provider.newFolder(rootPath);