Add background-wide file metadata cache.

ui/file_manager/file_manager/common/js/importer_common.js

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // Shared cloud importer namespace
 var importer = importer || {};
 
 /** @enum {string} */
 importer.ScanEvent = {
   FINALIZED: 'finalized',
@@ skipping 625 matching lines @@
  * @return {string}
  */
 importer.inflateAppUrl = function(deflated) {
   if (deflated.substring(0, 1) === '$') {
     return importer.APP_URL_PREFIX_ + deflated.substring(1);
   }
   return deflated;
 };
 
 /**
- * @param {!FileEntry} fileEntry
- * @return {!Promise<string>} Resolves with a "hashcode" consisting of
- *     just the last modified time and the file size.
- */
-importer.createMetadataHashcode = function(fileEntry) {
-  var entry = new importer.PromisingFileEntry(fileEntry);
-  return new Promise(
-      /**
-       * @param {function()} resolve
-       * @param {function()} reject
-       * @this {importer.PersistentImportHistory}
-       */
-      function(resolve, reject) {
-        entry.getMetadata()
-            .then(
-                /**
-                 * @param {!Object} metadata
-                 * @return {!Promise<string>}
-                 * @this {importer.PersistentImportHistory}
-                 */
-                function(metadata) {
-                  if (!('modificationTime' in metadata)) {
-                    reject('File entry missing "modificationTime" field.');
-                  } else if (!('size' in metadata)) {
-                    reject('File entry missing "size" field.');
-                  } else {
-                    var secondsSinceEpoch =
-                        importer.toSecondsFromEpoch(metadata.modificationTime);
-                    resolve(secondsSinceEpoch + '_' + metadata.size);
-                  }
-                }.bind(this));
-      }.bind(this))
-      .catch(importer.getLogger().catcher('importer-common-create-hashcode'));
-};
-
-/**
  * @param {string} date A date string in the form
  *     expected by Date.parse.
  * @return {string} The number of seconds from epoch to the date...as a string.
  */
 importer.toSecondsFromEpoch = function(date) {
   // Since we're parsing a value that only has
   // precision to the second, our last three digits
   // will always be 000. We strip them and end up
   // with seconds.
   var milliseconds = String(Date.parse(date));
@@ skipping 400 matching lines @@
       });
 };
 
 /** @private @const {!importer.ChromeLocalStorage} */
 importer.ChromeLocalStorage.INSTANCE_ = new importer.ChromeLocalStorage();
 
 /** @return {!importer.ChromeLocalStorage} */
 importer.ChromeLocalStorage.getInstance = function() {
   return importer.ChromeLocalStorage.INSTANCE_;
 };