[filemanager] Allow user to select current directory when nothing in list is selected.

chrome/browser/resources/file_manager/js/file_manager.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.
 
 /**
  * FileManager constructor.
  *
  * FileManager objects encapsulate the functionality of the file selector
  * dialogs, as well as the full screen file manager application (though the
  * latter is not yet implemented).
@@ skipping 3439 matching lines @@
     var selectAllCheckbox =
         this.document_.getElementById('select-all-checkbox');
     if (selectAllCheckbox)
       this.updateSelectAllCheckboxState_(selectAllCheckbox);
   };
 
   FileManager.prototype.updateOkButton_ = function(event) {
     var selectable;
 
     if (this.dialogType_ == FileManager.DialogType.SELECT_FOLDER) {
-      selectable = this.selection.directoryCount == 1 &&
+      // In SELECT_FOLDER mode, we allow to select current directory
+      // when nothing is selected.
+      selectable = this.selection.directoryCount <= 1 &&
           this.selection.fileCount == 0;
     } else if (this.dialogType_ == FileManager.DialogType.SELECT_OPEN_FILE) {
       selectable = (this.isSelectionAvailable() &&
                     this.selection.directoryCount == 0 &&
                     this.selection.fileCount == 1);
     } else if (this.dialogType_ ==
                FileManager.DialogType.SELECT_OPEN_MULTI_FILE) {
       selectable = (this.isSelectionAvailable() &&
                     this.selection.directoryCount == 0 &&
                     this.selection.fileCount >= 1);
@@ skipping 814 matching lines @@
       }
 
       this.resolvePath(this.getCurrentDirectory() + '/' + filename,
           resolveCallback, resolveCallback);
       return;
     }
 
     var files = [];
     var selectedIndexes = this.currentList_.selectionModel.selectedIndexes;
 
+    if (this.dialogType_ == FileManager.DialogType.SELECT_FOLDER &&
+        selectedIndexes.length == 0) {
+      var url = this.getSearchOrCurrentDirectoryURL();
+      var singleSelection = {
+        urls: [url],
+        multiple: false,
+        filterIndex: this.getSelectedFilterIndex_(url)
+      };
+      this.selectFilesAndClose_(singleSelection);
+      return;
+    }
+
     // All other dialog types require at least one selected list item.
     // The logic to control whether or not the ok button is enabled should
     // prevent us from ever getting here, but we sanity check to be sure.
     if (!selectedIndexes.length)
       throw new Error('Nothing selected!');
 
     var dm = this.directoryModel_.getFileList();
     for (var i = 0; i < selectedIndexes.length; i++) {
       var entry = dm.item(selectedIndexes[i]);
       if (!entry) {
@@ skipping 322 matching lines @@
     function closeBanner() {
       self.cleanupGDataWelcome_();
       // Stop showing the welcome banner.
       localStorage[WELCOME_HEADER_COUNTER_KEY] = WELCOME_HEADER_COUNTER_LIMIT;
     }
 
     return maybeShowBanner;
   };
 })();