[Offline pages] Resetting offline page metadata store to handle LOAD/INIT failures

components/offline_pages/offline_page_metadata_store_sql.cc

Index: components/offline_pages/offline_page_metadata_store_sql.cc
diff --git a/components/offline_pages/offline_page_metadata_store_sql.cc b/components/offline_pages/offline_page_metadata_store_sql.cc
index 80061980d55d58f742b9bfecc9923f93021f6c6b..5941d553b524c8e6b296706354118aaad85a0e38 100644
--- a/components/offline_pages/offline_page_metadata_store_sql.cc
+++ b/components/offline_pages/offline_page_metadata_store_sql.cc
@@ -267,7 +267,7 @@ void NotifyLoadResult(scoped_refptr<base::SingleThreadTaskRunner> runner,
   } else {
     DVLOG(1) << "Offline pages database loading failed: " << status;
   }
-  runner->PostTask(FROM_HERE, base::Bind(callback, status, result));
+  runner->PostTask(FROM_HERE, base::Bind(callback, result));
 }
 
 void OpenConnectionSync(sql::Connection* db,
@@ -434,8 +434,12 @@ void ResetSync(sql::Connection* db,
                scoped_refptr<base::SingleThreadTaskRunner> runner,
                const base::Callback<void(StoreState)>& callback) {
   // This method deletes the content of the whole store and reinitializes it.
-  bool success = db->Raze();
-  db->Close();
+  bool success = true;
+  if (db) {
+    success = db->Raze();
+    db->Close();
+  }
+  success = base::DeleteFile(db_file_path, true /*recursive*/) && success;
   StoreState state;
   if (success) {
     state = InitDatabase(db, db_file_path) ? StoreState::LOADED

[jianli, 2016/11/15 21:48:38]

I think we should first get back to main thread upon destroying database. From
there, we should recreate sql::Connection instance, instead of reusing an
existing one, and then do the initialization. I have concern that some fields in
sql::Connection instance are not reset. For example, commit_time_histogram_ and
etc which might lead to incorrect data.

[fgorski, 2016/11/15 23:14:12]

Done.

@@ -455,7 +459,6 @@ OfflinePageMetadataStoreSQL::OfflinePageMetadataStoreSQL(
       db_file_path_(path.AppendASCII("OfflinePages.db")),
       state_(StoreState::NOT_LOADED),
       weak_ptr_factory_(this) {
-  OpenConnection();
 }
 
 OfflinePageMetadataStoreSQL::~OfflinePageMetadataStoreSQL() {
@@ -465,10 +468,21 @@ OfflinePageMetadataStoreSQL::~OfflinePageMetadataStoreSQL() {
   }
 }
 
+void OfflinePageMetadataStoreSQL::Initialize(
+    const InitializeCallback& callback) {
+  DCHECK(!db_);
+  db_.reset(new sql::Connection());
+  background_task_runner_->PostTask(
+      FROM_HERE,
+      base::Bind(&OpenConnectionSync, db_.get(),
+                 base::ThreadTaskRunnerHandle::Get(), db_file_path_,
+                 base::Bind(&OfflinePageMetadataStoreSQL::OnOpenConnectionDone,
+                            weak_ptr_factory_.GetWeakPtr(), callback)));
+}
+
 void OfflinePageMetadataStoreSQL::GetOfflinePages(
     const LoadCallback& callback) {
-  if (!CheckDb(base::Bind(
-          callback, STORE_INIT_FAILED, std::vector<OfflinePageItem>()))) {
+  if (!CheckDb(base::Bind(callback, std::vector<OfflinePageItem>()))) {
     return;
   }
 
@@ -523,15 +537,12 @@ void OfflinePageMetadataStoreSQL::RemoveOfflinePages(
                             base::ThreadTaskRunnerHandle::Get(), callback));
 }
 
-void OfflinePageMetadataStoreSQL::Reset(const ResetCallback& callback) {
-  if (!CheckDb(base::Bind(callback, false)))
-    return;
-
+void OfflinePageMetadataStoreSQL::Reset(const InitializeCallback& callback) {
   background_task_runner_->PostTask(
       FROM_HERE,
       base::Bind(&ResetSync, db_.get(), db_file_path_,
                  base::ThreadTaskRunnerHandle::Get(),
-                 base::Bind(&OfflinePageMetadataStoreSQL::OnResetDone,
+                 base::Bind(&OfflinePageMetadataStoreSQL::OnOpenConnectionDone,
                             weak_ptr_factory_.GetWeakPtr(), callback)));
 }
 
@@ -546,34 +557,18 @@ void OfflinePageMetadataStoreSQL::SetStateForTesting(StoreState state,
     db_.reset(nullptr);
 }
 
-void OfflinePageMetadataStoreSQL::OpenConnection() {
-  DCHECK(!db_);
-  db_.reset(new sql::Connection());
-  background_task_runner_->PostTask(
-      FROM_HERE,
-      base::Bind(&OpenConnectionSync, db_.get(),
-                 base::ThreadTaskRunnerHandle::Get(), db_file_path_,
-                 base::Bind(&OfflinePageMetadataStoreSQL::OnOpenConnectionDone,
-                            weak_ptr_factory_.GetWeakPtr())));
-}
-
-void OfflinePageMetadataStoreSQL::OnOpenConnectionDone(StoreState state) {
+void OfflinePageMetadataStoreSQL::OnOpenConnectionDone(
+    const InitializeCallback& callback,
+    StoreState state) {
   DCHECK(db_.get());
 
   state_ = state;
 
   // Unfortunately we were not able to open DB connection.
   if (state != StoreState::LOADED)
-    db_.reset();
-
-  // TODO(fgorski): This might be a place to start store recovery. Alternatively
-  // that can be attempted in the OfflinePageModel.
-}
+    db_.reset(nullptr);
 
-void OfflinePageMetadataStoreSQL::OnResetDone(const ResetCallback& callback,
-                                              StoreState state) {
-  OnOpenConnectionDone(state);
-  callback.Run(state == StoreState::LOADED);
+  callback.Run(state);
 }
 
 bool OfflinePageMetadataStoreSQL::CheckDb(const base::Closure& callback) {