Aura: Add --aura-laptop-mode to fill the workspace with a single window.

ui/aura_shell/root_window_layout_manager.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/root_window_layout_manager.h"
 
 #include "ui/aura/window.h"
 #include "ui/views/widget/widget.h"
 
 namespace aura_shell {
@@ skipping 14 matching lines @@
 // RootWindowLayoutManager, aura::LayoutManager implementation:
 
 void RootWindowLayoutManager::OnWindowResized() {
   gfx::Rect fullscreen_bounds =
       gfx::Rect(owner_->bounds().width(), owner_->bounds().height());
 
   aura::Window::Windows::const_iterator i;
   for (i = owner_->children().begin(); i != owner_->children().end(); ++i)
     (*i)->SetBounds(fullscreen_bounds);
 
-  background_widget_->SetBounds(fullscreen_bounds);
+  if (background_widget_)
+    background_widget_->SetBounds(fullscreen_bounds);
 }
 
 void RootWindowLayoutManager::OnWindowAddedToLayout(aura::Window* child) {
 }
 
 void RootWindowLayoutManager::OnWillRemoveWindowFromLayout(
     aura::Window* child) {
 }
 
 void RootWindowLayoutManager::OnChildWindowVisibilityChanged(
     aura::Window* child,
     bool visible) {
 }
 
 void RootWindowLayoutManager::SetChildBounds(
     aura::Window* child,
     const gfx::Rect& requested_bounds) {
   SetChildBoundsDirect(child, requested_bounds);
 }
 
 }  // namespace internal
 }  // namespace aura_shell