mus/ash: WmRootWindowController can be null in mus.

ash/shelf/shelf_layout_manager.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/shelf/shelf_layout_manager.h"
 
 #include <algorithm>
 #include <cmath>
 #include <cstring>
 #include <string>
@@ skipping 211 matching lines @@
       shelf_(shelf),
       workspace_controller_(NULL),
       window_overlaps_shelf_(false),
       mouse_over_shelf_when_auto_hide_timer_started_(false),
       bezel_event_filter_(new ShelfBezelEventFilter(this)),
       gesture_drag_status_(GESTURE_DRAG_NONE),
       gesture_drag_amount_(0.f),
       gesture_drag_auto_hide_state_(SHELF_AUTO_HIDE_SHOWN),
       update_shelf_observer_(NULL),
       chromevox_panel_height_(0),
-      duration_override_in_ms_(0),
-      root_window_controller_observer_(
-          new RootWindowControllerObserverImpl(this)) {
+      duration_override_in_ms_(0) {
   Shell::GetInstance()->AddShellObserver(this);
-  wm::WmWindowAura::Get(root_window_)
-      ->GetRootWindowController()
-      ->AddObserver(root_window_controller_observer_.get());
+
+  wm::WmRootWindowController* controller =
+      wm::WmWindowAura::Get(root_window_)->GetRootWindowController();
+  if (controller) {
+    root_window_controller_observer_.reset(
+        new RootWindowControllerObserverImpl(this));
+    controller->AddObserver(root_window_controller_observer_.get());
+  } else {
+    DCHECK(Shell::GetInstance()->in_mus());

[sky, 2016/04/28 15:23:12]

What about wrapping this whole thing in !Shell::GetInstance()->in_mus()?

[sadrul, 2016/04/28 15:28:51]

Done.

+  }
   Shell::GetInstance()->lock_state_controller()->AddObserver(this);
   aura::client::GetActivationClient(root_window_)->AddObserver(this);
   Shell::GetInstance()->session_state_delegate()->AddSessionStateObserver(this);
 }
 
 ShelfLayoutManager::~ShelfLayoutManager() {
   if (update_shelf_observer_)
     update_shelf_observer_->Detach();
 
   FOR_EACH_OBSERVER(ShelfLayoutManagerObserver, observers_, WillDeleteShelf());
   Shell::GetInstance()->RemoveShellObserver(this);
   Shell::GetInstance()->lock_state_controller()->RemoveObserver(this);
   Shell::GetInstance()->
       session_state_delegate()->RemoveSessionStateObserver(this);
-  wm::WmWindowAura::Get(root_window_)
-      ->GetRootWindowController()
-      ->RemoveObserver(root_window_controller_observer_.get());
+  if (root_window_controller_observer_) {
+    wm::WmWindowAura::Get(root_window_)
+        ->GetRootWindowController()
+        ->RemoveObserver(root_window_controller_observer_.get());
+  }
 }
 
 void ShelfLayoutManager::PrepareForShutdown() {
   // Clear all event filters, otherwise sometimes those filters may catch
   // synthesized mouse event and cause crashes during the shutdown.
   set_workspace_controller(NULL);
   auto_hide_event_filter_.reset();
   bezel_event_filter_.reset();
   // Stop observing window change, otherwise we can attempt to update a
   // partially destructed shelf.
@@ skipping 869 matching lines @@
   UpdateBoundsAndOpacity(target_bounds, true, NULL);
   UpdateVisibilityState();
 }
 
 void ShelfLayoutManager::UpdateShelfVisibilityAfterLoginUIChange() {
   UpdateVisibilityState();
   LayoutShelf();
 }
 
 }  // namespace ash