Implement "pinned" mode in ash.

ash/wm/maximize_mode/maximize_mode_window_state.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/maximize_mode/maximize_mode_window_state.h"
 
 #include <utility>
 
 #include "ash/aura/wm_window_aura.h"
 #include "ash/common/shell_window_ids.h"
@@ skipping 112 matching lines @@
 void MaximizeModeWindowState::OnWMEvent(wm::WindowState* window_state,
                                         const wm::WMEvent* event) {
   switch (event->type()) {
     case wm::WM_EVENT_TOGGLE_FULLSCREEN:
       ToggleFullScreen(window_state, window_state->delegate());
       break;
     case wm::WM_EVENT_FULLSCREEN:
       UpdateWindow(window_state, wm::WINDOW_STATE_TYPE_FULLSCREEN, true);
       break;
     case wm::WM_EVENT_PIN:
-      UpdateWindow(window_state, wm::WINDOW_STATE_TYPE_PINNED, true);
+      if (!WmShell::Get()->IsPinned())
+        UpdateWindow(window_state, wm::WINDOW_STATE_TYPE_PINNED, true);
       break;
     case wm::WM_EVENT_TOGGLE_MAXIMIZE_CAPTION:
     case wm::WM_EVENT_TOGGLE_VERTICAL_MAXIMIZE:
     case wm::WM_EVENT_TOGGLE_HORIZONTAL_MAXIMIZE:
     case wm::WM_EVENT_TOGGLE_MAXIMIZE:
     case wm::WM_EVENT_CYCLE_SNAP_DOCK_LEFT:
     case wm::WM_EVENT_CYCLE_SNAP_DOCK_RIGHT:
     case wm::WM_EVENT_CENTER:
     case wm::WM_EVENT_SNAP_LEFT:
     case wm::WM_EVENT_SNAP_RIGHT:
@@ skipping 173 matching lines @@
       // avoid flashing.
       if (window_state->IsMaximized())
         window_state->SetBoundsDirectCrossFade(bounds_in_parent);
       else
         window_state->SetBoundsDirectAnimated(bounds_in_parent);
     }
   }
 }
 
 }  // namespace ash