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

chrome/browser/cocoa/bookmark_bar_controller.mm

Index: chrome/browser/cocoa/bookmark_bar_controller.mm
===================================================================
--- chrome/browser/cocoa/bookmark_bar_controller.mm	(revision 30793)
+++ chrome/browser/cocoa/bookmark_bar_controller.mm	(working copy)
@@ -303,6 +303,17 @@
   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()