mash: remove more shell/shelf WmWindow usage.

ash/wm/overview/window_grid.cc

 // Copyright 2014 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/overview/window_grid.h"
 
 #include <algorithm>
 #include <functional>
 #include <set>
 #include <utility>
@@ skipping 624 matching lines @@
     (*iter)->OnMinimizedStateChanged();
     PositionWindows(false);
   }
 }
 
 void WindowGrid::InitShieldWidget() {
   // TODO(varkha): The code assumes that SHELF_BACKGROUND_MAXIMIZED is
   // synonymous with a black shelf background. Update this code if that
   // assumption is no longer valid.
   const float initial_opacity =
-      (WmShelf::ForWindow(root_window_)->GetBackgroundType() ==
+      (WmShelf::ForWindow(root_window_->aura_window())->GetBackgroundType() ==
        SHELF_BACKGROUND_MAXIMIZED)
           ? 1.f
           : 0.f;
   shield_widget_.reset(
       CreateBackgroundWidget(root_window_, ui::LAYER_SOLID_COLOR, kShieldColor,
                              0, 0, SK_ColorTRANSPARENT, initial_opacity));
   WmWindow* widget_window = WmWindow::Get(shield_widget_->GetNativeWindow());
   const gfx::Rect bounds = widget_window->GetParent()->GetBounds();
   widget_window->SetBounds(bounds);
   widget_window->aura_window()->SetName("OverviewModeShield");
@@ skipping 179 matching lines @@
         *min_right = left;
       if (*max_right < left)
         *max_right = left;
     }
     *max_bottom = top + height;
   }
   return windows_fit;
 }
 
 }  // namespace ash