aura: Make sure the desktop widget gets parented to the correct container.

ui/aura_shell/workspace/workspace_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/workspace/workspace_manager.h"
 
 #include <algorithm>
 
 #include "base/auto_reset.h"
 #include "ui/aura/desktop.h"
 #include "ui/aura/screen_aura.h"
@@ skipping 102 matching lines @@
     } else if (active_workspace_) {
       // Center the active workspace.
       int active_workspace_mid_x = (active_workspace_->bounds().x() +
           active_workspace_->bounds().width() / 2) * scale;
       dx = workspace_size_.width() / 2 - active_workspace_mid_x;
       dx = std::min(0, std::max(dx, workspace_size_.width() - overview_width));
     }
 
     transform.SetTranslateX(dx);
     transform.SetTranslateY(workspace_size_.height() *  (1.0f - scale) / 2);
-  } else {
+  } else if (active_workspace_) {
     transform.SetTranslateX(-active_workspace_->bounds().x());
   }
 
   viewport_->layer()->SetAnimation(aura::Window::CreateDefaultAnimation());
   viewport_->layer()->SetTransform(transform);
 }
 
 ////////////////////////////////////////////////////////////////////////////////
 // WorkspaceManager, Overridden from aura::DesktopObserver:
 
@@ skipping 64 matching lines @@
   // Move to active workspace.
   if (active_workspace_) {
     ui::Transform transform;
     transform.SetTranslateX(-active_workspace_->bounds().x());
     viewport_->layer()->SetAnimation(aura::Window::CreateDefaultAnimation());
     viewport_->SetTransform(transform);
   }
 }
 
 }  // namespace aura_shell