Delete desktop/shell instance correctly when chrome is shutting down

ui/aura_shell/shelf_layout_controller.cc

 // Copyright (c) 2011 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 "ui/aura_shell/shelf_layout_controller.h"
 
 #include "ui/aura/desktop.h"
 #include "ui/aura/screen_aura.h"
 #include "ui/gfx/compositor/layer.h"
 #include "ui/gfx/compositor/layer_animator.h"
@@ skipping 17 matching lines @@
       max_height_(-1),
       launcher_(launcher),
       status_(status) {
   gfx::Rect launcher_bounds = launcher->GetWindowScreenBounds();
   gfx::Rect status_bounds = status->GetWindowScreenBounds();
   max_height_ = std::max(launcher_bounds.height(), status_bounds.height());
   GetLayer(launcher)->GetAnimator()->AddObserver(this);
 }
 
 ShelfLayoutController::~ShelfLayoutController() {
-  GetLayer(launcher_)->GetAnimator()->RemoveObserver(this);
+  // Do not try to remove observer from layer as the Launcher is
+  // already deleted.
 }
 
 void ShelfLayoutController::LayoutShelf() {
   StopAnimating();
   TargetBounds target_bounds;
   float target_opacity = visible_ ? 1.0f : 0.0f;
   CalculateTargetBounds(visible_, &target_bounds);
   GetLayer(launcher_)->SetOpacity(target_opacity);
   GetLayer(status_)->SetOpacity(target_opacity);
   launcher_->SetBounds(target_bounds.launcher_bounds);
@@ skipping 60 matching lines @@
   animating_ = false;
   visible_ = !visible_;
   TargetBounds target_bounds;
   CalculateTargetBounds(visible_, &target_bounds);
   aura::Desktop::GetInstance()->screen()->set_work_area_insets(
       target_bounds.work_area_insets);
 }
 
 }  // internal
 }  // aura_shell