mojo leveldb: Get profile and leveldb connected to DOMStorageContext.

components/profile_service/leveldb_thread.h

+// Copyright 2016 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.
+
+#ifndef COMPONENTS_PROFILE_SERVICE_LEVELDB_THREAD_H_
+#define COMPONENTS_PROFILE_SERVICE_LEVELDB_THREAD_H_
+
+#include "base/macros.h"
+#include "base/memory/ref_counted.h"
+#include "base/memory/scoped_ptr.h"
+#include "base/threading/thread.h"
+#include "components/leveldb/public/interfaces/leveldb.mojom.h"
+#include "mojo/public/cpp/bindings/binding_set.h"
+#include "mojo/shell/public/cpp/message_loop_ref.h"
+
+namespace profile {
+
+// A separate thread for leveldb.
+//
+// In the profile application, we need to put leveldb service on its own thread
+// because otherwise it can deadlock with the profile service. (The leveldb
+// service asks the profile service for a directory and blocks, but if we
+// didn't put leveldb on its own thread, it would block its own thread.)
+class LevelDBThread : public base::Thread,
+                      public base::RefCountedThreadSafe<LevelDBThread> {
+ public:
+  LevelDBThread(scoped_ptr<mojo::MessageLoopRef> message_loop_ref,
+                mojo::InterfaceRequest<leveldb::LevelDBService> request);
+
+  // Passes |request| from the caller thread to our LevelDBThread and
+  // binds |request| to the leveldb service thread.
+  void BindNewRequest(mojo::InterfaceRequest<leveldb::LevelDBService> request);
+
+ private:
+  friend class base::RefCountedThreadSafe<LevelDBThread>;
+  ~LevelDBThread() override;
+
+  // Check on each connection error whether we have no more connections.
+  void OnServiceError();
+
+  // Implementation of BindNewRequest run on the LevelDBThread.
+  void BindNewRequestImpl(
+      mojo::InterfaceRequest<leveldb::LevelDBService> request);
+
+  // Overridden from base::SimpleThread:
+  void Init() override;
+  void CleanUp() override;
+
+  // A reference to the parent thread's message loop, which needs to stay alive
+  // while this thread is running. Set on the parent thread; destroyed on the
+  // child thread.
+  scoped_ptr<mojo::MessageLoopRef> parent_thread_message_loop_ref_;

[Ben Goodger (Google), 2016/03/11 23:21:38]

profile_service_message_loop_ref_?

// Hold a reference to the profile service's message loop to keep it alive as
long as there are LevelDB service bindings. Set on the parent thread...

+
+  // When we create our underlying LevelDBService, we want to give it a
+  // reference to this object's thread's message loop, so when the service goes
+  // away, this thread gets cleaned up which releases our reference to our
+  // parent thread.
+  mojo::MessageLoopRefFactory thread_message_loop_ref_;

[Ben Goodger (Google), 2016/03/11 23:21:38]

Shorter:

// The lifetime of the leveldb thread's message loop is tied to the lifetime of
the level db service it vends.

+
+  // The service shared between all requestors.
+  scoped_ptr<leveldb::LevelDBService> leveldb_service_;
+
+  // All outstanding references to the LevelDBService.
+  scoped_ptr<mojo::BindingSet<leveldb::LevelDBService>> leveldb_bindings_;
+
+  // Used to pass the initial request from the parent thread to the child
+  // thread.
+  mojo::InterfaceRequest<leveldb::LevelDBService> initial_leveldb_request_;
+
+  DISALLOW_COPY_AND_ASSIGN(LevelDBThread);
+};
+
+}  // namespace profile
+
+#endif  // COMPONENTS_PROFILE_SERVICE_LEVELDB_THREAD_H_