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

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

Index: chrome/browser/resources/file_manager/js/file_manager.js
===================================================================
--- chrome/browser/resources/file_manager/js/file_manager.js	(revision 142373)
+++ chrome/browser/resources/file_manager/js/file_manager.js	(working copy)
@@ -3457,7 +3457,9 @@
     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() &&
@@ -4292,6 +4294,18 @@
     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.