Extract ContentScanner from DirectoryContent.

chrome/browser/resources/file_manager/js/directory_model.js

 // Copyright (c) 2012 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.
 
 'use strict';
 
 // If directory files changes too often, don't rescan directory more than once
 // per specified interval
 var SIMULTANEOUS_RESCAN_INTERVAL = 1000;
 // Used for operations that require almost instant rescan.
@@ skipping 472 matching lines @@
                                                   opt_callback) {
   if (this.currentDirContents_.isScanning())
     this.currentDirContents_.cancelScan();
   this.currentDirContents_ = newDirContents;
   this.clearRescanTimeout_();
 
   if (this.pendingScan_)
     this.pendingScan_ = false;
 
   if (this.runningScan_) {
-    this.runningScan_.cancelScan();
+    if (this.runningScan_.isScanning())
+      this.runningScan_.cancelScan();
     this.runningScan_ = null;
   }
 
   var onDone = function() {
     cr.dispatchSimpleEvent(this, 'scan-completed');
     if (opt_callback)
       opt_callback();
   }.bind(this);
 
   var onFailed = function() {
@@ skipping 688 matching lines @@
       // handles the rescan if necessary.
       driveRoot = null;
     }
 
     var specialSearchType = PathUtil.getRootType(path);
     var searchOption;
     var dirEntry;
     if (specialSearchType == RootType.DRIVE_OFFLINE) {
       dirEntry = DirectoryModel.fakeDriveOfflineEntry_;
       searchOption =
-          DirectoryContentsDriveSearchMetadata.SearchType.SEARCH_OFFLINE;
+          DriveMetadataSearchContentScanner.SearchType.SEARCH_OFFLINE;
     } else if (specialSearchType == RootType.DRIVE_SHARED_WITH_ME) {
       dirEntry = DirectoryModel.fakeDriveSharedWithMeEntry_;
       searchOption =
-          DirectoryContentsDriveSearchMetadata.SearchType.SEARCH_SHARED_WITH_ME;
+          DriveMetadataSearchContentScanner.SearchType.SEARCH_SHARED_WITH_ME;
     } else if (specialSearchType == RootType.DRIVE_RECENT) {
       dirEntry = DirectoryModel.fakeDriveRecentEntry_;
       searchOption =
-          DirectoryContentsDriveSearchMetadata.SearchType.SEARCH_RECENT_FILES;
+          DriveMetadataSearchContentScanner.SearchType.SEARCH_RECENT_FILES;
 
     } else {
       // Unknown path.
       this.changeDirectory(PathUtil.DEFAULT_DIRECTORY);
       return;
     }
 
     var newDirContents = new DirectoryContentsDriveSearchMetadata(
         this.currentFileListContext_,
         driveRoot,
@@ skipping 26 matching lines @@
   if (this.onSearchCompleted_) {
     this.removeEventListener('scan-completed', this.onSearchCompleted_);
     this.onSearchCompleted_ = null;
   }
 
   if (this.onClearSearch_) {
     this.onClearSearch_();
     this.onClearSearch_ = null;
   }
 };