mash: Partially migrate WorkspaceController to ash common.

ash/aura/wm_root_window_controller_aura.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 "ash/aura/wm_root_window_controller_aura.h"
 
 #include "ash/aura/wm_shelf_aura.h"
 #include "ash/aura/wm_shell_aura.h"
 #include "ash/aura/wm_window_aura.h"
 #include "ash/common/wm/workspace/workspace_layout_manager_backdrop_delegate.h"
@@ skipping 58 matching lines @@
 
 bool WmRootWindowControllerAura::HasShelf() {
   return root_window_controller_->shelf_widget() != nullptr;
 }
 
 WmShell* WmRootWindowControllerAura::GetShell() {
   return WmShell::Get();
 }
 
 wm::WorkspaceWindowState WmRootWindowControllerAura::GetWorkspaceWindowState() {
+  if (!root_window_controller_->workspace_controller())
+    return wm::WORKSPACE_WINDOW_STATE_DEFAULT;
   return root_window_controller_->workspace_controller()->GetWindowState();
 }
 
 void WmRootWindowControllerAura::SetMaximizeBackdropDelegate(
     std::unique_ptr<WorkspaceLayoutManagerBackdropDelegate> delegate) {
   root_window_controller_->workspace_controller()->SetMaximizeBackdropDelegate(
       std::move(delegate));
 }
 
 AlwaysOnTopController* WmRootWindowControllerAura::GetAlwaysOnTopController() {
@@ skipping 63 matching lines @@
     const display::Display& display) {}
 
 void WmRootWindowControllerAura::OnDisplayMetricsChanged(
     const display::Display& display,
     uint32_t metrics) {
   FOR_EACH_OBSERVER(WmRootWindowControllerObserver, observers_,
                     OnWorkAreaChanged());
 }
 
 }  // namespace ash