[Background Sync] Use Mojo IPC to fire background sync events

content/browser/service_worker/service_worker_mojo_event_dispatcher.cc

+// 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.
+
+#include "content/browser/service_worker/service_worker_mojo_event_dispatcher.h"
+
+#include "content/public/browser/browser_thread.h"
+#include "content/public/browser/render_process_host.h"
+#include "content/public/common/service_registry.h"
+#include "third_party/mojo/src/mojo/public/cpp/bindings/interface_ptr_info.h"
+
+namespace content {
+
+namespace {
+
+// Converts mojo enum content::ServiceWorkerEventStatus values to Chromium
+// content::ServiceWorkerStatusCode values.
+// TODO(iclelland): Make these enums equivalent so that conversion can be a
+// static cast.
+ServiceWorkerStatusCode statusCodeFromMojoStatus(
+    ServiceWorkerEventStatus status) {
+  ServiceWorkerStatusCode status_code = SERVICE_WORKER_OK;
+  if (status == SERVICE_WORKER_EVENT_STATUS_COMPLETED) {
+    status_code = SERVICE_WORKER_OK;
+  } else if (status == SERVICE_WORKER_EVENT_STATUS_REJECTED) {
+    status_code = SERVICE_WORKER_ERROR_EVENT_WAITUNTIL_REJECTED;
+  } else if (status == SERVICE_WORKER_EVENT_STATUS_ABORT) {
+    status_code = SERVICE_WORKER_ERROR_ABORT;
+  } else {
+    NOTREACHED();
+  }
+  return status_code;
+}
+
+// Establishes a connection to a mojo service, and then transfers the local
+// endpoint of the message pipe to the IO thread so that it can be called from
+// there in the future without switching threads.
+//
+// On success, the callback is called with a detached InterfacePtrInfo, which
+// can be used to build a new InterfacePtr on the calling thread. Failure is
+// indicated by calling the callback with an invalid InterfacePtrInfo.
+//
+// This function must be called on the UI thread, as it accesses the service
+// registry member of the RenderProcessHost.
+template <typename MojoServiceType>
+void ConnectOnUIThread(
+    int render_process_id,
+    const base::Callback<void(mojo::InterfacePtrInfo<MojoServiceType>)>&
+        callback) {
+  DCHECK_CURRENTLY_ON(BrowserThread::UI);
+  mojo::InterfacePtr<MojoServiceType> mojo_interface_ptr;
+
+  RenderProcessHost* host = RenderProcessHost::FromID(render_process_id);
+  if (host) {
+    content::ServiceRegistry* registry = host->GetServiceRegistry();
+    if (registry) {
+      registry->ConnectToRemoteService(mojo::GetProxy(&mojo_interface_ptr));
+    }
+  }
+  BrowserThread::PostTask(
+      BrowserThread::IO, FROM_HERE,
+      base::Bind(callback, base::Passed(mojo_interface_ptr.PassInterface())));
+}
+
+}  // namespace
+
+ServiceWorkerMojoEventDispatcher::ServiceWorkerMojoEventDispatcher()
+    : weak_ptr_factory_(this) {
+  DCHECK_CURRENTLY_ON(BrowserThread::IO);
+}
+
+ServiceWorkerMojoEventDispatcher::~ServiceWorkerMojoEventDispatcher() {
+  DCHECK_CURRENTLY_ON(BrowserThread::IO);
+}
+
+void ServiceWorkerMojoEventDispatcher::DispatchSyncEvent(
+    int render_process_id,
+    int thread_id,
+    const ServiceWorkerVersion::StatusCallback& callback) {
+  DCHECK_CURRENTLY_ON(BrowserThread::IO);
+
+  if (!background_sync_client_.get()) {
+    // If we have not connected to the mojo service before, switch to the UI
+    // thread to connect, and then dispatch the event once the connection is
+    // established.
+    BrowserThread::PostTask(

[jkarlin, 2015/06/17 15:17:29]

This is much better, thanks! One more suggestion. You can have ConnectOnUIThread
return the MojoInterfacePtr instead of dealing with a callback, like so:

  BrowserThread::PostTaskAndReplyWithResult(
      BrowserThread::UI,
      FROM_HERE,
      base::Bind(&ConnectOnUIThread<BackgroundSyncServiceClient>,
                 render_process_id),
     
base::Bind(&ServiceWorkerMojoEventDispatcher::BindChannelAndDispatchSyncEvent,
                 weak_ptr_factory_.GetWeakPtr(),
                 thread_id, callback));

Not sure why the formatting above gets messed up, but you get the idea.

[iclelland, 2015/06/18 16:01:14]

That's a good API -- thanks for that pointer!

+        BrowserThread::UI, FROM_HERE,
+        base::Bind(
+            &ConnectOnUIThread<BackgroundSyncServiceClient>, render_process_id,
+            base::Bind(&ServiceWorkerMojoEventDispatcher::
+                           BindChannelAndDispatchSyncEvent,
+                       weak_ptr_factory_.GetWeakPtr(), thread_id, callback)));
+    return;
+  }
+  DispatchSyncEventInternal(thread_id, callback);
+}
+
+void ServiceWorkerMojoEventDispatcher::BindChannelAndDispatchSyncEvent(
+    int thread_id,
+    const ServiceWorkerVersion::StatusCallback& callback,
+    mojo::InterfacePtrInfo<BackgroundSyncServiceClient> mojo_interface_ptr) {
+  DCHECK_CURRENTLY_ON(BrowserThread::IO);
+  if (!background_sync_client_.get()) {
+    // If the connect call failed, mojo_interface_ptr will be an invalid
+    // pointer, so abort now.
+    if (!mojo_interface_ptr.is_valid()) {
+      OnEventFinished(callback, SERVICE_WORKER_EVENT_STATUS_ABORT);
+      return;
+    }
+    background_sync_client_.Bind(mojo_interface_ptr.Pass());
+  }
+  DispatchSyncEventInternal(thread_id, callback);
+}
+
+void ServiceWorkerMojoEventDispatcher::DispatchSyncEventInternal(
+    int thread_id,
+    const ServiceWorkerVersion::StatusCallback& callback) {
+  DCHECK_CURRENTLY_ON(BrowserThread::IO);
+
+  // TODO(iclelland): Replace this with the real event registration details
+  // crbug.com/482066
+  content::SyncRegistrationPtr null_event(content::SyncRegistration::New());
+
+  background_sync_client_->Sync(
+      null_event.Pass(), thread_id,
+      base::Bind(&ServiceWorkerMojoEventDispatcher::OnEventFinished,

[jkarlin, 2015/06/17 15:17:29]

Why not just pass the callback here? What purpose does OnEventFinished serve?

[iclelland, 2015/06/18 16:01:14]

The only thing it does currently is convert the callback result (a mojo
ServiceWorkerEventStatus) into something useful for the browser process (a
content::ServiceWorkerStatusCode). I haven't found a way to make the two types
identical, so I've added this to perform the conversion.

If we move the callback accounting into this class, then this will also be where
that cleanup happens. (But that's for the future)

+                 weak_ptr_factory_.GetWeakPtr(), callback));
+}
+
+void ServiceWorkerMojoEventDispatcher::OnEventFinished(
+    const ServiceWorkerVersion::StatusCallback& callback,
+    ServiceWorkerEventStatus result) {
+  DCHECK_CURRENTLY_ON(BrowserThread::IO);
+  callback.Run(statusCodeFromMojoStatus(result));
+}
+
+}  // namespace content