Sets the background color of shelf is opaque black when maximized (2nd)

ash/root_window_controller.cc

 // Copyright (c) 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/root_window_controller.h"
 
 #include <vector>
 
 #include "ash/ash_constants.h"
 #include "ash/ash_switches.h"
@@ skipping 340 matching lines @@
   // panel_layout_manager_ needs to be shut down before windows are destroyed.
   if (panel_layout_manager_) {
     panel_layout_manager_->Shutdown();
     panel_layout_manager_ = NULL;
   }
 
   // TODO(harrym): Remove when Status Area Widget is a child view.
   shelf_->ShutdownStatusAreaWidget();
 
   if (shelf_->shelf_layout_manager())
-    shelf_->shelf_layout_manager()->set_workspace_controller(NULL);
+    shelf_->shelf_layout_manager()->PrepareForShutdown();
 
   // Close background widget first as it depends on tooltip.
   wallpaper_controller_.reset();
   animating_wallpaper_controller_.reset();
 
   workspace_controller_.reset();
   aura::client::SetTooltipClient(root_window_.get(), NULL);
 
   while (!root_window_->children().empty()) {
     aura::Window* child = root_window_->children()[0];
@@ skipping 342 matching lines @@
 
 void RootWindowController::OnTouchHudProjectionToggled(bool enabled) {
   if (enabled)
     EnableTouchHudProjection();
   else
     DisableTouchHudProjection();
 }
 
 }  // namespace internal
 }  // namespace ash