service worker: Avoid starting up for activation during shutdown

content/browser/service_worker/service_worker_process_manager.cc

 // Copyright 2014 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 "content/browser/service_worker/service_worker_process_manager.h"
 
 #include <stddef.h>
 
 #include <algorithm>
 #include <utility>
@@ skipping 51 matching lines @@
 ServiceWorkerProcessManager::~ServiceWorkerProcessManager() {
   DCHECK_CURRENTLY_ON(BrowserThread::UI);
   DCHECK(IsShutdown())
       << "Call Shutdown() before destroying |this|, so that racing method "
       << "invocations don't use a destroyed BrowserContext.";
   DCHECK(instance_info_.empty());
 }
 
 void ServiceWorkerProcessManager::Shutdown() {
   DCHECK_CURRENTLY_ON(BrowserThread::UI);
-  browser_context_ = NULL;
+  {
+    base::AutoLock lock(browser_context_lock_);
+    browser_context_ = nullptr;
+  }
+
   for (std::map<int, ProcessInfo>::const_iterator it = instance_info_.begin();
        it != instance_info_.end();
        ++it) {
     RenderProcessHost::FromID(it->second.process_id)->DecrementWorkerRefCount();
   }
   instance_info_.clear();
 }
 
+bool ServiceWorkerProcessManager::IsShutdown() {
+  base::AutoLock lock(browser_context_lock_);
+  return !browser_context_;
+}
+
 void ServiceWorkerProcessManager::AddProcessReferenceToPattern(
     const GURL& pattern, int process_id) {
   if (!BrowserThread::CurrentlyOn(BrowserThread::UI)) {
     BrowserThread::PostTask(
         BrowserThread::UI,
         FROM_HERE,
         base::Bind(&ServiceWorkerProcessManager::AddProcessReferenceToPattern,
                    weak_this_,
                    pattern,
                    process_id));
@@ skipping 232 matching lines @@
 namespace std {
 // Destroying ServiceWorkerProcessManagers only on the UI thread allows the
 // member WeakPtr to safely guard the object's lifetime when used on that
 // thread.
 void default_delete<content::ServiceWorkerProcessManager>::operator()(
     content::ServiceWorkerProcessManager* ptr) const {
   content::BrowserThread::DeleteSoon(
       content::BrowserThread::UI, FROM_HERE, ptr);
 }
 }  // namespace std