Introduce the PlatformNotificationContext class.

content/browser/notifications/platform_notification_context.h

+// Copyright 2015 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 CONTENT_BROWSER_NOTIFICATIONS_PLATFORM_NOTIFICATION_CONTEXT_H_
+#define CONTENT_BROWSER_NOTIFICATIONS_PLATFORM_NOTIFICATION_CONTEXT_H_
+
+#include <stdint.h>
+
+#include "base/callback.h"
+#include "base/files/file_path.h"
+#include "base/memory/ref_counted.h"
+#include "content/common/content_export.h"
+
+class GURL;
+
+namespace base {
+class SequencedTaskRunner;
+}
+
+namespace content {
+
+class NotificationDatabase;
+struct NotificationDatabaseData;
+
+// Implementation of the Web Notification storage context.
+//
+// Represents the per-BrowserContext data for persistent Web Notifications.
+// The methods defined in this interface must only be called on the IO thread.
+class CONTENT_EXPORT PlatformNotificationContext
+    : public base::RefCountedThreadSafe<PlatformNotificationContext> {

[Bernhard Bauer, 2015/03/13 16:51:18]

Is there a particular reason this class needs to be refcounted? If it's just to
be able to post tasks to other threads, an alternative might be to split this
class up into an outer class that lives on the IO thread, and an inner "Core"
that lives on the task runner thread.

[Peter Beverloo, 2015/03/13 16:57:07]

It will be owned by StoragePartitionImpl (like the other storage contexts), but
the NotificationMessageFilter will also want to access the class.

https://code.google.com/p/chromium/codesearch#chromium/src/content/browser/st...

Note that the definition of the public methods and types will eventually move to
the content/ API, but I'd like to do that when the churn is over.

[Bernhard Bauer, 2015/03/13 17:24:01]

Urgh, so many refcounted classes :-( But fair enough (assuming that
NotificationMessageFilter will keep a reference to it).

+ public:
+  // Constructs a new platform notification context. If |path| is non-empty, the
+  // database will be initialized in the "Platform Notifications" subdirectory
+  // of |path|. Otherwise, the database will be initialized in memory.
+  explicit PlatformNotificationContext(const base::FilePath& path);
+
+  using ReadResultCallback =
+      base::Callback<void(bool /* success */,
+                          const NotificationDatabaseData&)>;
+
+  using WriteResultCallback =
+      base::Callback<void(bool /* success */,
+                          int64_t /* notification_id */)>;
+
+  // Reads the data associated with |notification_id| belonging to |origin|
+  // from the database. |callback| will be invoked with the success status
+  // and a reference to the notification database data when completed.
+  void ReadNotificationData(int64_t notification_id,
+                            const GURL& origin,
+                            const ReadResultCallback& callback);
+
+  // Writes the data associated with a notification to a database. When this
+  // action completed, |callback| will be invoked with the success status and
+  // the persistent notification id when written successfully.
+  void WriteNotificationData(const GURL& origin,
+                             const NotificationDatabaseData& database_data,
+                             const WriteResultCallback& callback);
+
+ protected:

[Bernhard Bauer, 2015/03/13 16:51:18]

Why is this protected?

[Peter Beverloo, 2015/03/13 16:57:07]

Typo. Fixed!

+  friend class base::RefCountedThreadSafe<PlatformNotificationContext>;
+  friend class PlatformNotificationContextTest;
+
+  virtual ~PlatformNotificationContext();
+
+  // Initializes the database if neccesary. Must be called on the IO thread.
+  // |success_closure| will be invoked on a the thread which must be used to

[Bernhard Bauer, 2015/03/13 16:51:18]

The "the thread which must be used to access |database_|" is just the
|task_runner_| thread, right?

[Peter Beverloo, 2015/03/13 16:57:07]

Done.

+  // access |database_| when everything is available, or |failure_closure_|
+  // will be invoked on the IO thread when initialization fails.
+  void LazyInitialize(const base::Closure& success_closure,
+                      const base::Closure& failure_closure);
+
+  // Opens the database. Must be called on the |task_runner_| thread. When the
+  // database has been opened, |success_closure| will be invoked on the task
+  // thread, otherwise |failure_closure_ will be invoked on the IO thread.
+  void OpenDatabase(const base::Closure& success_closure,
+                    const base::Closure& failure_closure);
+
+  // Actually reads the notification data from the database. Must only be
+  // called on the |task_runner_| thread. Will post a task to |callback| on
+  // the IO thread when the operation has completed.
+  void DoReadNotificationData(int64_t notification_id,
+                              const GURL& origin,
+                              const ReadResultCallback& callback);
+
+  // Actually writes the notification database to the database. Must only be
+  // called on the |task_runner_| thread. Will post a task to |callback| on
+  // the IO thread when the operation has completed.
+  void DoWriteNotificationData(const GURL& origin,
+                               const NotificationDatabaseData& database_data,
+                               const WriteResultCallback& callback);
+
+  // Returns the path in which the database should be initialized. May be empty.
+  base::FilePath GetDatabasePath() const;
+
+  // Sets the task runner to use for testing purposes.
+  void SetTaskRunnerForTesting(
+      scoped_refptr<base::SequencedTaskRunner> task_runner);

[Bernhard Bauer, 2015/03/13 16:51:18]

Pass by const-ref?

[Peter Beverloo, 2015/03/13 16:57:07]

Done.

+
+  base::FilePath path_;
+
+  scoped_refptr<base::SequencedTaskRunner> task_runner_;
+  scoped_ptr<NotificationDatabase> database_;
+
+  int64_t next_notification_id_;
+
+  DISALLOW_COPY_AND_ASSIGN(PlatformNotificationContext);
+};
+
+}  // namespace content
+
+#endif  // CONTENT_BROWSER_NOTIFICATIONS_PLATFORM_NOTIFICATION_CONTEXT_H_