Implement "pinned" mode in ash.

ash/shelf/shelf_layout_manager.h

 // Copyright 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.
 
 #ifndef ASH_SHELF_SHELF_LAYOUT_MANAGER_H_
 #define ASH_SHELF_SHELF_LAYOUT_MANAGER_H_
 
 #include <memory>
 #include <vector>
 
@@ skipping 137 matching lines @@
 
   // Overridden from SnapLayoutManager:
   void OnWindowResized() override;
   void SetChildBounds(aura::Window* child,
                       const gfx::Rect& requested_bounds) override;
 
   // Overridden from ash::ShellObserver:
   void OnLockStateChanged(bool locked) override;
   void OnShelfAlignmentChanged(WmWindow* root_window) override;
   void OnShelfAutoHideBehaviorChanged(WmWindow* root_window) override;
+  void OnPinnedStateChanged(WmWindow* pinned_window) override;
 
   // Overriden from aura::client::ActivationChangeObserver:
   void OnWindowActivated(
       aura::client::ActivationChangeObserver::ActivationReason reason,
       aura::Window* gained_active,
       aura::Window* lost_active) override;
 
   // Overridden from ash::LockStateObserver:
   void OnLockStateEvent(LockStateObserver::EventType event) override;
 
@@ skipping 223 matching lines @@
 
   std::unique_ptr<RootWindowControllerObserverImpl>
       root_window_controller_observer_;
 
   DISALLOW_COPY_AND_ASSIGN(ShelfLayoutManager);
 };
 
 }  // namespace ash
 
 #endif  // ASH_SHELF_SHELF_LAYOUT_MANAGER_H_