Start pulling away notification logic from ChromeContentBrowserClient.

content/public/browser/platform_notification_service.h

+// Copyright 2014 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_PUBLIC_BROWSER_PLATFORM_NOTIFICATION_SERVICE_H_
+#define CONTENT_PUBLIC_BROWSER_PLATFORM_NOTIFICATION_SERVICE_H_
+
+#include "base/callback_forward.h"
+#include "base/memory/scoped_ptr.h"
+#include "content/common/content_export.h"
+#include "content/public/common/show_desktop_notification_params.h"
+#include "third_party/WebKit/public/platform/WebNotificationPermission.h"
+
+class GURL;
+
+namespace content {
+
+class BrowserContext;
+class DesktopNotificationDelegate;
+class ResourceContext;
+
+// The service using which notifications can be presented to the user. There
+// should be a unique instance of the PlatformNotificationService depending
+// on the browsing context being used.
+class CONTENT_EXPORT PlatformNotificationService {
+ public:
+  virtual ~PlatformNotificationService() {}
+
+  // Checks if |origin| has permission to display Web Notifications. This method
+  // must be called on the IO thread.
+  virtual blink::WebNotificationPermission CheckPermission(
+      ResourceContext* resource_context,
+      const GURL& origin,
+      int render_process_id) = 0;
+
+  // Displays the notification described in |params| to the user. This method
+  // must be called on the UI thread.
+  virtual void DisplayNotification(
+      BrowserContext* browser_context,
+      const ShowDesktopNotificationHostMsgParams& params,
+      scoped_ptr<DesktopNotificationDelegate> delegate,
+      int render_process_id,
+      base::Closure* cancel_callback) = 0;

[dewittj, 2014/12/02 17:22:59]

It's unclear that this is an outparam, can you document that, or even better
make it the return value?

[Peter Beverloo, 2014/12/05 20:03:43]

I've documented it in the comment. I don't think that returning the callback is
a great solution, mostly because the name implies that, if it were to return
anything, it'd be a boolean. A naive check like:

if (service_->DisplayNotification(...)) { }

would succeed just fine when returning the closure...

We could name it something verbose like
DisplayNotificationAndReturnCloseClosure, though.

+};
+
+}  // namespace content
+
+#endif  // CONTENT_PUBLIC_BROWSER_PLATFORM_NOTIFICATION_SERVICE_H_