Create an AutofillBackend interface

components/webdata/common/web_data_service_backend.cc

 // Copyright 2013 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 "components/webdata/common/web_data_service_backend.h"
 
 #include "base/bind.h"
 #include "base/location.h"
 #include "components/webdata/common/web_data_request_manager.h"
 #include "components/webdata/common/web_database.h"
@@ skipping 55 matching lines @@
   db_.reset(NULL);
   init_complete_ = !should_reinit; // Setting init_complete_ to true will ensure
   // that the init sequence is not re-run.
 
   init_status_ = sql::INIT_FAILURE;
 }
 
 void WebDataServiceBackend::DBWriteTaskWrapper(
     const WebDatabaseService::WriteTask& task,
     scoped_ptr<WebDataRequest> request) {
+  if (request->IsCancelled())
+    return;
+
+  ExecuteWriteTask(task);
+  request_manager_->RequestCompleted(request.Pass());
+}
+
+void WebDataServiceBackend::ExecuteWriteTask(
+    const WebDatabaseService::WriteTask& task) {
   LoadDatabaseIfNecessary();
-  if (db_ && init_status_ == sql::INIT_OK && !request->IsCancelled()) {
+  if (db_ && init_status_ == sql::INIT_OK) {
     WebDatabase::State state = task.Run(db_.get());
     if (state == WebDatabase::COMMIT_NEEDED)
       Commit();
   }
-  request_manager_->RequestCompleted(request.Pass());
 }
 
 void WebDataServiceBackend::DBReadTaskWrapper(
     const WebDatabaseService::ReadTask& task,
     scoped_ptr<WebDataRequest> request) {
-  LoadDatabaseIfNecessary();
-  if (db_ && init_status_ == sql::INIT_OK && !request->IsCancelled()) {
-    request->SetResult(task.Run(db_.get()).Pass());
-  }
+  if (request->IsCancelled())
+    return;
+
+  request->SetResult(ExecuteReadTask(task).Pass());
   request_manager_->RequestCompleted(request.Pass());
 }
 
+scoped_ptr<WDTypedResult> WebDataServiceBackend::ExecuteReadTask(
+    const WebDatabaseService::ReadTask& task) {
+  LoadDatabaseIfNecessary();
+  if (db_ && init_status_ == sql::INIT_OK) {
+    return task.Run(db_.get());
+  }
+  return scoped_ptr<WDTypedResult>(NULL);
+}
+
 WebDataServiceBackend::~WebDataServiceBackend() {
   ShutdownDatabase(false);
 }
 
 void WebDataServiceBackend::Commit() {
   if (db_ && init_status_ == sql::INIT_OK) {
     db_->CommitTransaction();
     db_->BeginTransaction();
   } else {
     NOTREACHED() << "Commit scheduled after Shutdown()";
   }
 }