Initial framework setup and skeleton for BackgroundFetchContext

content/browser/background_fetch/background_fetch_context.cc

+// Copyright 2017 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/background_fetch/background_fetch_context.h"
+
+#include "content/browser/service_worker/service_worker_context_wrapper.h"
+#include "content/public/browser/browser_thread.h"
+
+namespace content {
+
+BackgroundFetchContext::BackgroundFetchContext(
+    BrowserContext* browser_context,
+    const scoped_refptr<ServiceWorkerContextWrapper>& service_worker_context)
+    : browser_context_(browser_context),
+      service_worker_context_(service_worker_context) {
+  DCHECK_CURRENTLY_ON(BrowserThread::UI);
+
+  service_worker_context_->AddObserver(this);

[Peter Beverloo, 2017/02/09 15:48:55]

The Service Worker Context's observer list is thread-hostile, which here means
that we need to add and remove the observer on the thread that we want to
receive the methods on.

It seems to me like we'd want to receive OnRegistrationDeleted() on the IO
thread. That means we already need InitOnIO and ShutdownOnIO methods to make
sure we can register ourselves as the observer on the right thread.

However, perhaps we should punt that until a time where we'll start to use the
observer? It should be unit-testable.

[harkness, 2017/02/13 17:20:05]

I'll definitely look into this when I start cleaning up for those methods, but
that's a few steps down my road right now.

[Peter Beverloo, 2017/02/13 18:35:05]

Let's then have a TODO for registering an observer on the
|service_worker_context| as opposed to registering one we won't be able to use.

+}
+
+BackgroundFetchContext::~BackgroundFetchContext() {
+  DCHECK_CURRENTLY_ON(BrowserThread::UI);
+
+  service_worker_context_->RemoveObserver(this);
+}
+
+void BackgroundFetchContext::Init() {
+  DCHECK_CURRENTLY_ON(BrowserThread::UI);
+
+  // TODO(harkness) Create the Download observer.
+  // TODO(harkness) Create the Data manager.
+  // TODO(harkness) Create the Batch manager.
+}
+
+void BackgroundFetchContext::Shutdown() {
+  DCHECK_CURRENTLY_ON(BrowserThread::UI);
+
+  // TODO(harkness) Clean up all the things.
+}
+
+void BackgroundFetchContext::OnRegistrationDeleted(int64_t registration_id,
+                                                   const GURL& pattern) {
+  DCHECK_CURRENTLY_ON(BrowserThread::UI);
+  // TODO(harkness) Call into the data manager and delete metadata, this will
+  // a call to the DownloadManager to abort any ongoing downloads.
+}
+
+}  // namespace content