Move content/child/background_sync to Blink.

third_party/WebKit/Source/modules/background_sync/BackgroundSyncProvider.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 BackgroundSyncProvider_h
+#define BackgroundSyncProvider_h
+
+#include "modules/background_sync/SyncCallbacks.h"
+#include "public/platform/modules/background_sync/background_sync.mojom-blink.h"
+#include "public/platform/modules/serviceworker/WebServiceWorkerRegistration.h"

[Peter Beverloo, 2016/11/08 16:45:11]

micro nit: you can forward declare WebServiceWorkerRegistration instead.

[adithyas, 2016/11/08 18:26:19]

Done.

+#include "wtf/Noncopyable.h"
+#include <memory>
+#include <stdint.h>
+#include <string>

[Peter Beverloo, 2016/11/08 16:45:11]

nit: these three includes are unused.

[adithyas, 2016/11/08 18:26:19]

Done.

+
+namespace blink {
+
+// The BackgroundSyncProvider is called by the SyncManager and SyncRegistration
+// objects and communicates with the BackgroundSyncManager object in the browser
+// process. Each thread will have its own instance (e.g. main thread, worker
+// threads), instantiated as needed by SyncManager.  Each instance of
+// the provider creates a new mojo connection to a new
+// BackgroundSyncManagerImpl, which then talks to the BackgroundSyncManager
+// object.
+class BackgroundSyncProvider {

[Peter Beverloo, 2016/11/08 16:45:11]

BackgroundSyncProvider used to observe the WorkerThread (if any) to trigger its
own deletion, and use the lifetime of the BlinkPlatformImpl (tied to the
RenderThreadImpl) for instance on the main thread.

I can't quite figure out the new story. Since the instances are thread locals,
do we keep them around forever -- at least until the next navigation? Does that
mean that we may end up with unused Mojo handles for workers that no longer
exist?

(The BackgroundSyncContext keeps around instances until either the entire
context goes (i.e. the profile), or the service had a connection error.)

Other features, e.g. Web Payments and Notifications, make sure that the class
owning the connection can be garbage collected when the context goes away. Is
there a reason not to use that same pattern here?

[jbroman, 2016/11/08 17:39:32]

WTF::ThreadSpecific dies when the thread dies.
That said, I suggested in a previous comment that this could be merged into the
GC-ed SyncManager in a followup CL (along with SyncCallbacks, since the
implementations that pass to ScriptPromiseResolver could be in that source file,
too).

[adithyas, 2016/11/08 18:26:19]

My initial implementation did have one instance of BackgroundSyncProvider per
SyncManager instance (which would mean BackgroundSyncProvider got GCed along
with SyncManager) but I wasn't sure if it was semantically the same thing as the
current implementation (there could be multiple SyncManagers per thread?)

+  WTF_MAKE_NONCOPYABLE(BackgroundSyncProvider);
+
+ public:
+  BackgroundSyncProvider() = default;
+
+  void registerBackgroundSync(mojom::blink::SyncRegistrationPtr options,
+                              WebServiceWorkerRegistration*,
+                              std::unique_ptr<SyncRegistrationCallbacks>);
+  void getRegistrations(WebServiceWorkerRegistration*,
+                        std::unique_ptr<SyncGetRegistrationsCallbacks>);
+
+ private:
+  // Callback handlers
+  static void registerCallback(
+      std::unique_ptr<blink::SyncRegistrationCallbacks>,
+      mojom::blink::BackgroundSyncError,
+      mojom::blink::SyncRegistrationPtr options);
+  static void getRegistrationsCallback(
+      std::unique_ptr<SyncGetRegistrationsCallbacks>,
+      mojom::blink::BackgroundSyncError,
+      mojo::WTFArray<mojom::blink::SyncRegistrationPtr> registrations);
+
+  // Helper method that returns an initialized BackgroundSyncServicePtr.
+  mojom::blink::BackgroundSyncServicePtr& GetBackgroundSyncServicePtr();
+
+  mojom::blink::BackgroundSyncServicePtr m_backgroundSyncService;
+};
+
+}  // namespace blink
+
+#endif  // BackgroundSyncProvider_h