Ensure that the callback for MetadataCache.getOne() is called asynchronously.

ui/file_manager/file_manager/foreground/js/metadata/metadata_cache.js

Index: ui/file_manager/file_manager/foreground/js/metadata/metadata_cache.js
diff --git a/ui/file_manager/file_manager/foreground/js/metadata/metadata_cache.js b/ui/file_manager/file_manager/foreground/js/metadata/metadata_cache.js
index e991451208acadfaf94cc8d2157062333850675c..79e19e2c57a82e6f328afdeabfda9ab75f8cc2c7 100644
--- a/ui/file_manager/file_manager/foreground/js/metadata/metadata_cache.js
+++ b/ui/file_manager/file_manager/foreground/js/metadata/metadata_cache.js
@@ -199,9 +199,10 @@ MetadataCache.prototype.currentEvictionThreshold_ = function() {
  * @param {Array.<Entry>} entries The list of entries.
  * @param {string} type The metadata type.
  * @param {function(Object)} callback The metadata is passed to callback.
+ *     The callback is called asynchronously.
  */
 MetadataCache.prototype.get = function(entries, type, callback) {
-  return this.getInternal_(entries, type, false, callback);
+  this.getInternal_(entries, type, false, callback);
 };
 
 /**
@@ -211,9 +212,10 @@ MetadataCache.prototype.get = function(entries, type, callback) {
  * @param {Array.<Entry>} entries The list of entries.
  * @param {string} type The metadata type.
  * @param {function(Object)} callback The metadata is passed to callback.
+ *     The callback is called asynchronously.
  */
 MetadataCache.prototype.getLatest = function(entries, type, callback) {
-  return this.getInternal_(entries, type, true, callback);
+  this.getInternal_(entries, type, true, callback);
 };
 
 /**
@@ -224,11 +226,12 @@ MetadataCache.prototype.getLatest = function(entries, type, callback) {
  * @param {boolean} refresh True to get the latest value and refresh the cache,
  *     false to get the value from the cache.
  * @param {function(Object)} callback The metadata is passed to callback.
+ *     The callback is called asynchronously.
  */
 MetadataCache.prototype.getInternal_ =
     function(entries, type, refresh, callback) {
   if (entries.length === 0) {
-    if (callback) callback([]);
+    if (callback) setTimeout(callback.bind(null, []), 0);
     return;
   }
 
@@ -241,7 +244,7 @@ MetadataCache.prototype.getInternal_ =
     remaining--;
     if (remaining === 0) {
       this.endBatchUpdates();
-      if (callback) setTimeout(callback, 0, result);
+      if (callback) callback(result);
     }
   };
 
@@ -256,12 +259,14 @@ MetadataCache.prototype.getInternal_ =
 
 /**
  * Fetches the metadata for one Entry. See comments to |get|.
+ *
  * @param {Entry} entry The entry.
  * @param {string} type Metadata type.
- * @param {function(Object)} callback The callback.
+ * @param {function(Object)} callback The metadata is passed to callback.
+ *     The callback is called asynchronously.
  */
 MetadataCache.prototype.getOne = function(entry, type, callback, refresh) {
-  return this.getOneInternal_(entry, type, false, callback);
+  this.getOneInternal_(entry, type, false, callback);
 };
 
 /**
@@ -271,7 +276,8 @@ MetadataCache.prototype.getOne = function(entry, type, callback, refresh) {
  * @param {string} type Metadata type.
  * @param {boolean} refresh True to get the latest value and refresh the cache,
  *     false to get the value from the cache.
- * @param {function(Object)} callback The callback.
+ * @param {function(Object)} callback The metadata is passed to callback.
+ *     The callback is called asynchronously.
  * @private
  */
 MetadataCache.prototype.getOneInternal_ =
@@ -306,7 +312,7 @@ MetadataCache.prototype.getOneInternal_ =
 
   if (!refresh && type in item.properties) {
     // Uses cache, if available and not on the 'refresh' mode.
-    callback(item.properties[type]);
+    setTimeout(callback.bind(null, item.properties[type]), 0);
     return;
   }
 
@@ -354,7 +360,7 @@ MetadataCache.prototype.getOneInternal_ =
   var tryNextProvider = function() {
     if (providers.length === 0) {
       self.endBatchUpdates();
-      callback(item.properties[type] || null);
+      setTimeout(callback.bind(null, item.properties[type] || null), 0);
       return;
     }
 
@@ -684,7 +690,7 @@ MetadataProvider.prototype.isInitialized = function() { return true; };
  * @param {Entry} entry File entry.
  * @param {string} type Requested metadata type.
  * @param {function(Object)} callback Callback expects a map from metadata type
- *     to metadata value.
+ *     to metadata value. This callback must be called asynchronously.
  */
 MetadataProvider.prototype.fetch = function(entry, type, callback) {
   throw new Error('Default metadata provider cannot fetch.');
@@ -731,7 +737,7 @@ FilesystemProvider.prototype.getId = function() { return 'filesystem'; };
  * @param {Entry} entry File entry.
  * @param {string} type Requested metadata type.
  * @param {function(Object)} callback Callback expects a map from metadata type
- *     to metadata value.
+ *     to metadata value. This callback is called asynchronously.
  */
 FilesystemProvider.prototype.fetch = function(
     entry, type, callback) {
@@ -809,7 +815,7 @@ DriveProvider.prototype.getId = function() { return 'drive'; };
  * @param {Entry} entry File entry.
  * @param {string} type Requested metadata type.
  * @param {function(Object)} callback Callback expects a map from metadata type
- *     to metadata value.
+ *     to metadata value. This callback is called asynchronously.
  */
 DriveProvider.prototype.fetch = function(entry, type, callback) {
   this.entries_.push(entry);
@@ -994,11 +1000,11 @@ ContentProvider.prototype.getId = function() { return 'content'; };
  * @param {Entry} entry File entry.
  * @param {string} type Requested metadata type.
  * @param {function(Object)} callback Callback expects a map from metadata type
- *     to metadata value.
+ *     to metadata value. This callback is called asynchronously.
  */
 ContentProvider.prototype.fetch = function(entry, type, callback) {
   if (entry.isDirectory) {
-    callback({});
+    setTimeout(callback.bind(null, {}), 0);
     return;
   }
   var entryURL = entry.toURL();