Files.app: Add createSnapshot, clone, hasFreashCache methods to metadata models.

ui/file_manager/file_manager/foreground/js/metadata/metadata_cache_set_unittest.js

Index: ui/file_manager/file_manager/foreground/js/metadata/metadata_cache_set_unittest.js
diff --git a/ui/file_manager/file_manager/foreground/js/metadata/metadata_cache_set_unittest.js b/ui/file_manager/file_manager/foreground/js/metadata/metadata_cache_set_unittest.js
index 6d3b8a43f559c0de4125a4a806aa385abc4faf25..c429e6586fa03b99d075802d69b70a0e54000a16 100644
--- a/ui/file_manager/file_manager/foreground/js/metadata/metadata_cache_set_unittest.js
+++ b/ui/file_manager/file_manager/foreground/js/metadata/metadata_cache_set_unittest.js
@@ -82,3 +82,43 @@ function testMetadataCacheSetInvalidatePartial() {
   assertEquals(1, loadRequested[0].names.length);
   assertEquals('property', loadRequested[0].names[0]);
 }
+
+function testMetadataCacheSetCreateSnapshot() {
+  var setA = new MetadataCacheSet(new MetadataCacheSetStorageForObject({}));
+  setA.startRequests(1, setA.createRequests([entryA, entryB], ['property']));
+  var setB = setA.createSnapshot([entryA]);
+  setA.storeProperties(
+      1, [entryA, entryB], [{property: 'valueA'}, {property: 'valueB'}]);
+  var results = setB.get([entryA, entryB], ['property']);
+  assertEquals(2, results.length);
+  assertEquals(null, results[0].property);
+  assertEquals(undefined, results[1].property);
+
+  setB.storeProperties(
+      1, [entryA, entryB], [{property: 'valueA'}, {property: 'valueB'}]);
+  var results = setB.get([entryA, entryB], ['property']);
+  assertEquals(2, results.length);
+  assertEquals('valueA', results[0].property);
+  assertEquals(undefined, results[1].property);
+
+  setA.invalidate(2, [entryA, entryB]);
+  var results = setB.get([entryA, entryB], ['property']);
+  assertEquals(2, results.length);
+  assertEquals('valueA', results[0].property);
+  assertEquals(undefined, results[1].property);
+}
+
+function testMetadataCacheSetHasFreshCache() {
+  var set = new MetadataCacheSet(new MetadataCacheSetStorageForObject({}));
+  assertFalse(set.hasFreshCache([entryA, entryB], ['property']));
+
+  set.startRequests(1, set.createRequests([entryA, entryB], ['property']));
+  set.storeProperties(
+      1, [entryA, entryB], [{property: 'valueA'}, {property: 'valueB'}]);
+  assertTrue(set.hasFreshCache([entryA, entryB], ['property']));
+
+  set.invalidate(2, [entryB]);
+  assertFalse(set.hasFreshCache([entryA, entryB], ['property']));
+
+  assertTrue(set.hasFreshCache([entryA], ['property']));
+}