Refine ash shelf tooltip closing on non-mash ChromeOS.

ash/shelf/shelf_widget.cc

 // Copyright 2012 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 "ash/shelf/shelf_widget.h"
 
 #include "ash/ash_switches.h"
 #include "ash/focus_cycler.h"
 #include "ash/root_window_controller.h"
 #include "ash/session/session_state_delegate.h"
@@ skipping 262 matching lines @@
       case ash::SHELF_ALIGNMENT_RIGHT:
         return gfx::Insets(0, distance, 0, 0);
       case ash::SHELF_ALIGNMENT_TOP:
         return gfx::Insets(0, 0, distance, 0);
     }
     NOTREACHED();
     return gfx::Insets();
   }
 
   // ash::ShelfLayoutManagerObserver:
-  void WillDeleteShelf() override { shelf_ = NULL; }
+  void WillDeleteShelf() override {
+    shelf_->RemoveObserver(this);
+    shelf_ = NULL;
+  }
 
   void WillChangeVisibilityState(ash::ShelfVisibilityState new_state) override {
     gfx::Insets mouse_insets;
     gfx::Insets touch_insets;
     if (new_state == ash::SHELF_VISIBLE) {
       // Let clicks at the very top of the shelf through so windows can be
       // resized with the bottom-right corner and bottom edge.
       mouse_insets = GetInsetsForAlignment(
           ShelfLayoutManager::kWorkspaceAreaVisibleInset,
           shelf_->GetAlignment());
@@ skipping 538 matching lines @@
   DCHECK(delegate_view_);
   return delegate_view_->disable_dimming_animations_for_test();
 }
 
 void ShelfWidget::WillDeleteShelf() {
   shelf_layout_manager_->RemoveObserver(this);
   shelf_layout_manager_ = NULL;
 }
 
 }  // namespace ash