Watchdog entries caused by toolbar module.

Problem/Motivation

If you install standard you will watchdog entries on every request:

Theme hook toolbar_item not found.

This was caused by a "merge conflict" between:

#2226207: Make 'template' the default output option for hook_theme()

diff --git a/core/modules/toolbar/toolbar.module b/core/modules/toolbar/toolbar.module
index fb47469..3d960a8 100644
--- a/core/modules/toolbar/toolbar.module
+++ b/core/modules/toolbar/toolbar.module
@@ -42,9 +42,6 @@ function toolbar_theme($existing, $type, $theme, $path) {
     'render element' => 'element',
     'template' => 'toolbar',
   );
-  $items['toolbar_item'] = array(
-    'render element' => 'element',
-  );
 
   return $items;
 }

and #2326895: Convert toolbar_element_info() to Element classes

Proposed resolution

Drop the line:
'#theme' => 'toolbar_item',from ToolbarItem.

Remaining tasks

User interface changes

API changes