Implement "pinned" mode in ash.

ash/wm/workspace_controller.cc

 // Copyright (c) 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.
 
 #include "ash/wm/workspace_controller.h"
 
 #include <utility>
 
 #include "ash/aura/wm_window_aura.h"
 #include "ash/common/shell_window_ids.h"
 #include "ash/common/wm/window_state.h"
 #include "ash/common/wm/workspace/workspace_layout_manager.h"
 #include "ash/common/wm/workspace/workspace_layout_manager_backdrop_delegate.h"
 #include "ash/common/wm/workspace/workspace_layout_manager_delegate.h"
+#include "ash/common/wm_shell.h"
 #include "ash/root_window_controller.h"
 #include "ash/shelf/shelf_layout_manager.h"
 #include "ash/shell.h"
 #include "ash/wm/window_animations.h"
 #include "ash/wm/window_state_aura.h"
 #include "ash/wm/window_util.h"
 #include "ash/wm/workspace/workspace_event_handler.h"
 #include "base/memory/ptr_util.h"
 #include "ui/aura/client/aura_constants.h"
 #include "ui/aura/window.h"
@@ skipping 26 matching lines @@
       shelf_(NULL),
       event_handler_(new WorkspaceEventHandler),
       layout_manager_(new WorkspaceLayoutManager(WmWindowAura::Get(viewport),
                                                  std::move(delegate))) {
   SetWindowVisibilityAnimationTransition(
       viewport_, ::wm::ANIMATE_NONE);
 
   WmWindowAura::Get(viewport_)->SetLayoutManager(
       base::WrapUnique(layout_manager_));
   viewport_->AddPreTargetHandler(event_handler_.get());
+  WmShell::Get()->AddShellObserver(layout_manager_);
 }
 
 WorkspaceController::~WorkspaceController() {
+  WmShell::Get()->RemoveShellObserver(layout_manager_);
+  viewport_->RemovePreTargetHandler(event_handler_.get());
   viewport_->SetLayoutManager(NULL);
-  viewport_->RemovePreTargetHandler(event_handler_.get());
 }
 
 wm::WorkspaceWindowState WorkspaceController::GetWindowState() const {
   if (!shelf_)
     return wm::WORKSPACE_WINDOW_STATE_DEFAULT;
   const aura::Window* topmost_fullscreen_window = GetRootWindowController(
       viewport_->GetRootWindow())->GetWindowForFullscreenMode();
   if (topmost_fullscreen_window &&
       !wm::GetWindowState(topmost_fullscreen_window)->ignored_by_shelf()) {
     return wm::WORKSPACE_WINDOW_STATE_FULL_SCREEN;
@@ skipping 64 matching lines @@
     viewport_->layer()->SetOpacity(1.0f);
   }
 }
 
 void WorkspaceController::SetMaximizeBackdropDelegate(
     std::unique_ptr<WorkspaceLayoutManagerBackdropDelegate> delegate) {
   layout_manager_->SetMaximizeBackdropDelegate(std::move(delegate));
 }
 
 }  // namespace ash