Check default_container in FramePainter::UseSoloWindowHeader

ash/wm/frame_painter.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/wm/frame_painter.h"
 
 #include "ash/shell.h"
 #include "ash/shell_window_ids.h"
 #include "ash/wm/window_util.h"
 #include "base/logging.h"  // DCHECK
@@ skipping 528 matching lines @@
       window_icon_->bounds().right() + kTitleIconOffsetX :
       kTitleNoIconOffsetX;
 }
 
 bool FramePainter::UseSoloWindowHeader(aura::Window* ignore) const {
   // In unit tests this can be called after the shell is destroyed.
   if (!Shell::HasInstance())
     return false;
   const aura::Window* default_container = Shell::GetInstance()->GetContainer(
       internal::kShellWindowId_DefaultContainer);
+  if (!default_container)
+    return false;  // Shutting down. See crbug.com/120786.
   int normal_window_count = 0;
   const aura::Window::Windows& windows = default_container->children();
   for (aura::Window::Windows::const_iterator it = windows.begin();
        it != windows.end();
        ++it) {
     if (*it != ignore && IsVisibleNormalWindow(*it)) {
       normal_window_count++;
       if (normal_window_count > 1)
         return false;
     }
   }
   return normal_window_count == 1;
 }
 
 }  // namespace ash