ServiceWorker: Check liveness of ServiceWorkerDatabase before deletin…

…g an old diskcache

After diskcache migration, ServiceWorkerStorage posts a delayed task to delete
an old diskcache and to record the result in ServiceWorkerDatabase. This task
accesses the database without any liveness check, so the task possibly crashes
if the database is closed before that.

This CL makes the task to confirm the liveness before accessing the database.

BUG=487482,505333

Review URL: https://codereview.chromium.org/1210073009

Cr-Commit-Position: refs/heads/master@{#336951}

content/browser/service_worker/service_worker_storage.cc

@@ -1434,9 +1434,9 @@ ServiceWorkerDiskCache* ServiceWorkerStorage::disk_cache() {
   if (old_disk_cache_deletion_needed_) {
     // Lazily delete the old diskcache.
     BrowserThread::PostAfterStartupTask(
-        FROM_HERE, database_task_manager_->GetTaskRunner(),
-        base::Bind(&DeleteOldDiskCacheInDB, database_.get(),
-                   GetOldDiskCachePath()));
+        FROM_HERE, base::ThreadTaskRunnerHandle::Get(),
+        base::Bind(&ServiceWorkerStorage::DeleteOldDiskCache,
+                   weak_factory_.GetWeakPtr()));
   }
 
   ServiceWorkerMetrics::RecordDiskCacheMigrationResult(
@@ -1470,9 +1470,9 @@ void ServiceWorkerStorage::DidSetDiskCacheMigrationNotNeeded(
 
   // Lazily delete the old diskcache and update the database.
   BrowserThread::PostAfterStartupTask(
-      FROM_HERE, database_task_manager_->GetTaskRunner(),
-      base::Bind(&DeleteOldDiskCacheInDB, database_.get(),
-                 GetOldDiskCachePath()));
+      FROM_HERE, base::ThreadTaskRunnerHandle::Get(),
+      base::Bind(&ServiceWorkerStorage::DeleteOldDiskCache,
+                 weak_factory_.GetWeakPtr()));
 
   ServiceWorkerMetrics::RecordDiskCacheMigrationResult(
       ServiceWorkerMetrics::MIGRATION_OK);
@@ -1513,6 +1513,15 @@ void ServiceWorkerStorage::OnDiskCacheInitialized(int rv) {
   ServiceWorkerMetrics::CountInitDiskCacheResult(rv == net::OK);
 }
 
+void ServiceWorkerStorage::DeleteOldDiskCache() {
+  DCHECK(state_ == INITIALIZED || state_ == DISABLED) << state_;
+  if (IsDisabled())
+    return;
+  database_task_manager_->GetTaskRunner()->PostTask(
+      FROM_HERE, base::Bind(&ServiceWorkerStorage::DeleteOldDiskCacheInDB,
+                            database_.get(), GetOldDiskCachePath()));
+}
+
 void ServiceWorkerStorage::StartPurgingResources(
     const std::vector<int64>& ids) {
   DCHECK(has_checked_for_stale_resources_);

content/browser/service_worker/service_worker_storage.h

@@ -405,6 +405,8 @@ class CONTENT_EXPORT ServiceWorkerStorage
   void InitializeDiskCache();
   void OnDiskCacheInitialized(int rv);
 
+  void DeleteOldDiskCache();
+
   void StartPurgingResources(const std::vector<int64>& ids);
   void StartPurgingResources(const ResourceList& resources);
   void ContinuePurgingResources();