Added AddDownload communication path and observers

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 "base/memory/ptr_util.h"
 #include "content/browser/background_fetch/background_fetch_client_proxy.h"
 #include "content/browser/background_fetch/background_fetch_data_manager.h"
 #include "content/browser/background_fetch/background_fetch_event_dispatcher.h"
@@ skipping 27 matching lines @@
 
 BackgroundFetchContext::BackgroundFetchContext(
     BrowserContext* browser_context,
     StoragePartitionImpl* storage_partition,
     scoped_refptr<ServiceWorkerContextWrapper> service_worker_context)
     : browser_context_(browser_context),
       data_manager_(
           base::MakeUnique<BackgroundFetchDataManager>(browser_context)),
       event_dispatcher_(base::MakeUnique<BackgroundFetchEventDispatcher>(
           std::move(service_worker_context))),
-      client_proxy_(base::MakeUnique<BackgroundFetchClientProxy>(this)) {
+      client_proxy_(
+          base::MakeUnique<BackgroundFetchClientProxy>(browser_context, this)) {
   DCHECK_CURRENTLY_ON(BrowserThread::UI);
   BackgroundFetchClient* background_fetch_client =
       browser_context_->GetBackgroundFetchClient();
   if (background_fetch_client)
     background_fetch_client->SetDelegate(client_proxy_.get());
 }
 
 BackgroundFetchContext::~BackgroundFetchContext() {
   DCHECK_CURRENTLY_ON(BrowserThread::UI);
 }
@@ skipping 37 matching lines @@
     std::vector<scoped_refptr<BackgroundFetchRequestInfo>> initial_requests) {
   RecordRegistrationCreatedError(error);
   if (error != blink::mojom::BackgroundFetchError::NONE) {
     callback.Run(error, base::nullopt /* registration */);
     return;
   }
 
   // Create the BackgroundFetchJobController, which will do the actual fetching.
   CreateController(registration_id, options, std::move(initial_requests));
 
+  // Tell the BackgroundFetchClient that a job has started, which will allow
+  // embedders to display updates.
+  BrowserThread::PostTask(BrowserThread::IO, FROM_HERE,
+                          base::Bind(&BackgroundFetchClientProxy::AddDownload,
+                                     client_proxy_->GetWeakPtr(),
+                                     registration_id.Serialize(), options));

[Peter Beverloo, 2017/04/20 16:27:55]

I'd like to encapsulate the thread-jumps to the BackgroundFetchClientProxy.
Based on the contract defined in the class-level comment it's fine to call these
methods on the IO thread.

In order to make this fully safe, we should:

    1) Initialise the BackgroundFetchClientProxy on the UI thread, have it store
the BackgroundFetchClient pointer. (Retrieved from the BrowserContext.)
    2) In BackgroundFetchContext::Shutdown, call through to the BGFCP where we
set the client_ to a nullptr.
    3) For calls like this,
        a) Call BGFCP::AddFrobinator() on the IO thread. Jump to
BGFCP::AddFrobinatorOnUI w/ a WeakPtr.
        b) Check if client_ is not a nullptr. Make the call if so.

Downside is needing two methods per call, but it avoids making the assumption
that the browser_context will remain alive, while also avoiding lots of null
checks here or in the JobController.

[Peter Beverloo, 2017/04/20 16:27:55]

Should the JobController make this call? It has better knowledge of the state of
an in-progress fetch than the context.

[Peter Beverloo, 2017/04/24 14:39:14]

Ping.

+
   // Create the BackgroundFetchRegistration the renderer process will receive,
   // which enables it to resolve the promise telling the developer it worked.
   BackgroundFetchRegistration registration;
   registration.tag = registration_id.tag();
   registration.icons = options.icons;
   registration.title = options.title;
   registration.total_download_size = options.total_download_size;
 
   callback.Run(blink::mojom::BackgroundFetchError::NONE, registration);
 }
@@ skipping 132 matching lines @@
   // TODO(harkness): pass the command to the JobController for the given task.
 }
 
 void BackgroundFetchContext::ResumeFetch(
     const BackgroundFetchRegistrationId& registration_id) {
   DCHECK_CURRENTLY_ON(BrowserThread::IO);
   // TODO(harkness): pass the command to the JobController for the given task.
 }
 
 }  // namespace content