Now that the launcher is sized to the width of the root window we need

ui/aura_shell/shelf_layout_manager.h

 // 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.
 
 #ifndef UI_AURA_SHELL_SHELF_LAYOUT_MANAGER_H_
 #define UI_AURA_SHELL_SHELF_LAYOUT_MANAGER_H_
 #pragma once
 
 #include "base/basictypes.h"
 #include "base/compiler_specific.h"
 #include "ui/aura/layout_manager.h"
 #include "ui/aura_shell/aura_shell_export.h"
 #include "ui/gfx/compositor/layer_animation_observer.h"
 #include "ui/gfx/insets.h"
 #include "ui/gfx/rect.h"
 
 namespace views {
 class Widget;
 }
 
 namespace aura_shell {
 namespace internal {
 
-// ShelfLayoutManager is a layout manager responsible for the launcher.
-// Also supports showing and hiding the launcher/status area
-// as well as positioning them.
-// Exported for unit tests.
+// ShelfLayoutManager is the layout manager responsible for the launcher and
+// status widgets. The launcher is given the total available width and told the
+// width of the status area. This allows the launcher to draw the background and
+// layout to the status area.
+// To respond to bounds changes in the status area StatusAreaLayoutManager works
+// closely with ShelfLayoutManager.
 class AURA_SHELL_EXPORT ShelfLayoutManager : public aura::LayoutManager,
                                              public ui::LayerAnimationObserver {
  public:
   ShelfLayoutManager(views::Widget* launcher, views::Widget* status);
   virtual ~ShelfLayoutManager();
 
   bool in_layout() const { return in_layout_; }
 
   // Stops any animations and sets the bounds of the launcher and status
   // widgets.
@@ skipping 62 matching lines @@
   views::Widget* launcher_;
   views::Widget* status_;
 
   DISALLOW_COPY_AND_ASSIGN(ShelfLayoutManager);
 };
 
 }  // namespace internal
 }  // namespace aura_shell
 
 #endif  // UI_AURA_SHELL_SHELF_LAYOUT_MANAGER_H_