Start to use new metadata item in ImageEncoder.

ui/file_manager/gallery/js/gallery_item_unittest.js

Index: ui/file_manager/gallery/js/gallery_item_unittest.js
diff --git a/ui/file_manager/gallery/js/gallery_item_unittest.js b/ui/file_manager/gallery/js/gallery_item_unittest.js
index e3c545b28593bb85fecba06b6eb8620a5e1956fc..d2a4e179be2a6c934d5bd88b49e7fd1c5f53a631 100644
--- a/ui/file_manager/gallery/js/gallery_item_unittest.js
+++ b/ui/file_manager/gallery/js/gallery_item_unittest.js
@@ -63,6 +63,13 @@ function testSaveToFile(callback) {
       {isReadOnly: false},
       {name: 'oldMetadata'},
       metadataCache,
+      // Mock of FileSystemMetadata.
+      {
+        get: function() {
+          return Promise.resolve({});
+        },
+        notifyEntriesChanged: function() {}
+      },
       /* original */ true);
   assertEquals('oldMetadata', item.getMetadata().name);
   assertFalse(fetchedMediaCleared);