Implement "pinned" mode in ash.

ash/common/wm/default_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/common/wm/default_state.h"
 
 #include "ash/common/shell_window_ids.h"
 #include "ash/common/wm/dock/docked_window_layout_manager.h"
 #include "ash/common/wm/window_animation_types.h"
 #include "ash/common/wm/window_parenting_utils.h"
@@ skipping 187 matching lines @@
     case WM_EVENT_DOCK:
       next_state_type = WINDOW_STATE_TYPE_DOCKED;
       break;
     case WM_EVENT_SET_BOUNDS:
       SetBounds(window_state, static_cast<const SetBoundsEvent*>(event));
       return;
     case WM_EVENT_SHOW_INACTIVE:
       next_state_type = WINDOW_STATE_TYPE_INACTIVE;
       break;
     case WM_EVENT_PIN:
-      // TODO(hidehiko): Check if the window can be pinnable. If a system modal
-      // window is openening, or if there already is another pinned window,
-      // the pinning should fail.
-      next_state_type = WINDOW_STATE_TYPE_PINNED;
+      // If there already is a pinned window, it is not allowed to set it
+      // to this window.
+      // TODO(hidehiko): If a system modal window is openening, the pinning
+      // probably should fail.
+      if (WmShell::Get()->IsPinned()) {
+        LOG(ERROR) << "An PIN event is triggered, while another window is "
+                   << "already in pinned mode.";
+        next_state_type = current_state_type;
+      } else {
+        next_state_type = WINDOW_STATE_TYPE_PINNED;
+      }
       break;
     case WM_EVENT_TOGGLE_MAXIMIZE_CAPTION:
     case WM_EVENT_TOGGLE_MAXIMIZE:
     case WM_EVENT_TOGGLE_VERTICAL_MAXIMIZE:
     case WM_EVENT_TOGGLE_HORIZONTAL_MAXIMIZE:
     case WM_EVENT_TOGGLE_FULLSCREEN:
     case WM_EVENT_CYCLE_SNAP_DOCK_LEFT:
     case WM_EVENT_CYCLE_SNAP_DOCK_RIGHT:
     case WM_EVENT_CENTER:
       NOTREACHED() << "Compound event should not reach here:" << event;
@@ skipping 520 matching lines @@
     gfx::Rect center_in_parent = GetDisplayWorkAreaBoundsInParent(window);
     center_in_parent.ClampToCenteredSize(window->GetBounds().size());
     window_state->SetBoundsDirectAnimated(center_in_parent);
   }
   // Centering window is treated as if a user moved and resized the window.
   window_state->set_bounds_changed_by_user(true);
 }
 
 }  // namespace wm
 }  // namespace ash