arc: Fix crash in arc_process_task.cc during browser shutdown

chrome/browser/task_manager/providers/arc/arc_process_task.cc

 // Copyright 2015 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 "chrome/browser/task_manager/providers/arc/arc_process_task.h"
 
 #include "base/bind.h"
 #include "base/i18n/rtl.h"
 #include "base/strings/string_number_conversions.h"
 #include "base/strings/utf_string_conversions.h"
@@ skipping 95 matching lines @@
   if (result == arc::ActivityIconLoader::GetResult::FAILED_ARC_NOT_READY) {
     // Need to retry loading the icon.
     arc::ArcServiceManager::Get()
         ->arc_bridge_service()
         ->intent_helper()
         ->AddObserver(this);
   }
 }
 
 ArcProcessTask::~ArcProcessTask() {
-  arc::ArcServiceManager::Get()
-      ->arc_bridge_service()
-      ->intent_helper()
-      ->RemoveObserver(this);
+  auto* service_manager = arc::ArcServiceManager::Get();
+  // This destructor can also be called when TaskManagerImpl is destructed.
+  // Since TaskManagerImpl is a LAZY_INSTANCE, arc::ArcServiceManager may have
+  // already been destructed. In that case, arc_bridge_service() has also been
+  // destructed, and it is safe to just return.
+  if (!service_manager)
+    return;
+  service_manager->arc_bridge_service()->intent_helper()->RemoveObserver(this);
 }
 
 Task::Type ArcProcessTask::GetType() const {
   return Task::ARC;
 }
 
 int ArcProcessTask::GetChildProcessUniqueID() const {
   // ARC process is not a child process of the browser.
   return content::ChildProcessHost::kInvalidUniqueID;
 }
@@ skipping 40 matching lines @@
   for (const auto& kv : *icons) {
     const gfx::Image& icon = kv.second.icon16;
     if (icon.IsEmpty())
       continue;
     set_icon(*icon.ToImageSkia());
     break;  // Since the parent class can hold only one icon, break here.
   }
 }
 
 }  // namespace task_manager