[MD Bookmarks] Prevent sorting of empty folders.

This CL disables the sort button in the toolbar action menu for empty
folders.

BUG=737034
CQ_INCLUDE_TRYBOTS=master.tryserver.chromium.linux:closure_compilation

Review-Url: https://codereview.chromium.org/2973783002
Cr-Commit-Position: refs/heads/master@{#485563}

chrome/browser/resources/md_bookmarks/toolbar.html

@@ -64,9 +64,10 @@
     </cr-toolbar>
     <template is="cr-lazy-render" id="dropdown">
       <dialog is="cr-action-menu" role="menu">
-        <button class="dropdown-item"
+        <button id="sortButton"
+            class="dropdown-item"
             on-tap="onSortTap_"
-            disabled="[[!canChangeList_]]"
+            disabled="[[!canSortFolder_]]"
             role="menuitem">
           $i18n{menuSort}
         </button>

chrome/browser/resources/md_bookmarks/toolbar.js

@@ -43,6 +43,12 @@ Polymer({
     /** @private */
     selectedFolder_: String,
 
+    /** @private */
+    canSortFolder_: {
+      type: Boolean,
+      computed: 'computeCanSortFolder_(canChangeList_, selectedFolder_)',
+    },
+
     /** @private */
     canChangeList_: {
       type: Boolean,
@@ -84,8 +90,7 @@ Polymer({
 
   /** @private */
   onSortTap_: function() {
-    chrome.bookmarkManagerPrivate.sortChildren(
-        assert(this.getState().selectedFolder));
+    chrome.bookmarkManagerPrivate.sortChildren(assert(this.selectedFolder_));
     bookmarks.ToastManager.getInstance().show(
         loadTimeData.getString('toastFolderSorted'), true);
     this.closeDropdownMenu_();
@@ -95,7 +100,7 @@ Polymer({
   onAddBookmarkTap_: function() {
     var dialog =
         /** @type {BookmarksEditDialogElement} */ (this.$.addDialog.get());
-    dialog.showAddDialog(false, assert(this.getState().selectedFolder));
+    dialog.showAddDialog(false, assert(this.selectedFolder_));
     this.closeDropdownMenu_();
   },
 
@@ -103,7 +108,7 @@ Polymer({
   onAddFolderTap_: function() {
     var dialog =
         /** @type {BookmarksEditDialogElement} */ (this.$.addDialog.get());
-    dialog.showAddDialog(true, assert(this.getState().selectedFolder));
+    dialog.showAddDialog(true, assert(this.selectedFolder_));
     this.closeDropdownMenu_();
   },
 
@@ -121,7 +126,7 @@ Polymer({
 
   /** @private */
   onDeleteSelectionTap_: function() {
-    var selection = this.getState().selection.items;
+    var selection = this.selectedItems_;
     var commandManager = bookmarks.CommandManager.getInstance();
     assert(commandManager.canExecute(Command.DELETE, selection));
     commandManager.handle(Command.DELETE, selection);
@@ -158,6 +163,15 @@ Polymer({
     this.searchField.setValue(this.searchTerm_ || '');
   },
 
+  /**
+   * @return {boolean}
+   * @private
+   */
+  computeCanSortFolder_: function() {
+    return this.canChangeList_ &&
+        this.getState().nodes[this.selectedFolder_].children.length > 0;
+  },
+
   /**
    * @return {boolean}
    * @private

chrome/test/data/webui/md_bookmarks/toolbar_test.js

@@ -19,6 +19,12 @@ suite('<bookmarks-toolbar>', function() {
             createItem('2'),
             createItem('3'),
             createFolder('4', [], {unmodifiable: 'managed'}),
+            createFolder('5', []),
+            createFolder(
+                '6',
+                [
+                  createItem('61'),
+                ]),
           ])),
       selection: {
         items: new Set(),
@@ -108,4 +114,18 @@ suite('<bookmarks-toolbar>', function() {
     assertTrue(toolbar.$$('#addBookmarkButton').disabled);
     assertTrue(toolbar.$$('#importBookmarkButton').disabled);
   });
+
+  test('sort button is disabled when folder is empty', function() {
+    MockInteractions.tap(toolbar.$.menuButton);
+
+    store.data.selectedFolder = '6';
+    store.notifyObservers();
+    assertTrue(toolbar.canSortFolder_);
+
+    store.data.selectedFolder = '5';
+    store.notifyObservers();
+
+    assertFalse(toolbar.canSortFolder_);
+    assertTrue(toolbar.$$('#sortButton').disabled);
+  });
 });