Disable open all bookmarks context menu item if there are no bookmarks....

chrome/browser/cocoa/bookmark_bar_controller.mm

 // Copyright (c) 2009 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.
 
 #include "app/l10n_util_mac.h"
 #include "app/resource_bundle.h"
 #include "base/mac_util.h"
 #include "base/sys_string_conversions.h"
 #include "chrome/browser/bookmarks/bookmark_editor.h"
 #include "chrome/browser/bookmarks/bookmark_model.h"
@@ skipping 285 matching lines @@
 }
 
 - (BookmarkNode*)nodeFromButton:(id)button {
   NSCell* cell = [button cell];
   BookmarkNode* node = static_cast<BookmarkNode*>(
       [[cell representedObject] pointerValue]);
   DCHECK(node);
   return node;
 }
 
+// At this time, the only item which ever gets disabled is "Open All
+// Bookmarks".
+- (BOOL)validateUserInterfaceItem:(id<NSValidatedUserInterfaceItem>)item {
+  SEL action = [item action];
+  if ((action == @selector(openAllBookmarks:)) &&
+      (![buttons_ count])) {
+    return NO;
+  }
+  return YES;
+}
+
 - (IBAction)openBookmark:(id)sender {
   BookmarkNode* node = [self nodeFromButton:sender];
   [urlDelegate_ openBookmarkURL:node->GetURL()
                     disposition:event_utils::WindowOpenDispositionFromNSEvent(
                         [NSApp currentEvent])];
 }
 
 // Given a NSMenuItem tag, return the appropriate bookmark node id.
 - (int64)nodeIdFromMenuTag:(int32)tag {
   return menuTagMap_[tag];
@@ skipping 587 matching lines @@
 
 - (NSButton*)offTheSideButton {
   return offTheSideButton_;
 }
 
 - (NSButton*)otherBookmarksButton {
   return otherBookmarksButton_.get();
 }
 
 @end