Remove persisted docked windows

ui/views/mus/desktop_window_tree_host_mus.cc

 // Copyright 2016 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 "ui/views/mus/desktop_window_tree_host_mus.h"
 
 #include "base/memory/ptr_util.h"
 #include "base/threading/thread_task_runner_handle.h"
 #include "ui/aura/client/aura_constants.h"
 #include "ui/aura/client/cursor_client.h"
@@ skipping 185 matching lines @@
   // the cursor-client needs to be unset on the root-window before
   // |cursor_manager_| is destroyed.
   aura::client::SetCursorClient(window(), nullptr);
   native_widget_delegate_->AsWidget()->RemoveObserver(this);
   MusClient::Get()->RemoveObserver(this);
   aura::Env::GetInstance()->RemoveObserver(this);
   desktop_native_widget_aura_->OnDesktopWindowTreeHostDestroyed(this);
 }
 
 bool DesktopWindowTreeHostMus::IsDocked() const {
+  // TODO(afakhry): Remove in M58.
   return window()->GetProperty(aura::client::kShowStateKey) ==
          ui::SHOW_STATE_DOCKED;
 }
 
 void DesktopWindowTreeHostMus::SendClientAreaToServer() {
   if (!ShouldSendClientAreaToServer())
     return;
 
   NonClientView* non_client_view =
       native_widget_delegate_->AsWidget()->non_client_view();
@@ skipping 134 matching lines @@
   desktop_native_widget_aura_->OnHostClosed();
 }
 
 aura::WindowTreeHost* DesktopWindowTreeHostMus::AsWindowTreeHost() {
   return this;
 }
 
 void DesktopWindowTreeHostMus::ShowWindowWithState(ui::WindowShowState state) {
   if (state == ui::SHOW_STATE_MAXIMIZED || state == ui::SHOW_STATE_FULLSCREEN ||
       state == ui::SHOW_STATE_DOCKED) {
+    // TODO(afakhry): Remove in M58.
     window()->SetProperty(aura::client::kShowStateKey, state);
   }
   window()->Show();
   if (compositor())
     compositor()->SetVisible(true);
 
   native_widget_delegate_->OnNativeWidgetVisibilityChanged(true);
 
   if (native_widget_delegate_->CanActivate()) {
     if (state != ui::SHOW_STATE_INACTIVE)
@@ skipping 362 matching lines @@
     aura::client::FocusClient* focus_client,
     aura::Window* window) {
   if (window == this->window()) {
     desktop_native_widget_aura_->HandleActivationChanged(true);
   } else if (is_active_) {
     desktop_native_widget_aura_->HandleActivationChanged(false);
   }
 }
 
 }  // namespace views