Add the copresence component.

components/copresence/public/copresence_client.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 COMPONENTS_COPRESENCE_PUBLIC_COPRESENCE_CLIENT_H_
+#define COMPONENTS_COPRESENCE_PUBLIC_COPRESENCE_CLIENT_H_
+
+#include <string>
+#include <vector>
+
+#include "base/callback.h"
+#include "base/macros.h"
+#include "base/memory/scoped_ptr.h"
+#include "base/memory/weak_ptr.h"
+#include "components/copresence/proto/rpcs.pb.h"
+#include "components/copresence/public/copresence_client_delegate.h"
+
+namespace net {
+class URLContextGetter;
+}
+
+namespace copresence {
+
+class CopresenceClientDelegate;
+class RpcHandler;
+class WhispernetClient;
+
+struct PendingRequest {
+  PendingRequest(const copresence::ReportRequest& report,
+                 const std::string app_id,
+                 const StatusCallback& callback);
+  ~PendingRequest();
+
+  copresence::ReportRequest report;
+  std::string app_id;
+  StatusCallback callback;
+};
+
+// The CopresenceClient class is the central interface for Copresence
+// functionality. This class handles all the initialization and delegation of
+// copresence tasks. Any user of copresence only needs to interact with this
+// client.
+class CopresenceClient : public base::SupportsWeakPtr<CopresenceClient> {
+ public:
+  // We do not take ownership of the delegate but we do take ownership of the
+  // whispernet_client. This is because the whispernet_client is tied to this
+  // copresence client (and various objects that it owns) while no such
+  // restriction exists for the delegate. Theoretically a client could use the
+  // same delegate for multiple CopresenceClients, not the case a
+  // WhispernetClient.

[jochen (gone - plz use gerrit), 2014/07/31 14:27:06]

sorry, I still didn't fully understand it. I thought there's going to be exactly
one of CopresenceClient, WhispernetClient, and CopresenceClientDelegate per
browser context?

Or is there a global CopresenceClient and WhispernetClient, and a delegate per
browser context?

[jochen (gone - plz use gerrit), 2014/07/31 14:46:41]

i'm not really sure how to make this API a lot nicer. I guess the whispernet
client should conceptually be part of this component, but since it depends on
the pnacl extension it can't.

I compared it a bit to the network stack which is passed to content via the
browser context, as it's a similar heavy-weight subsystem.

Then again, I think it doesn't really matter.

What I think is important, however, is that //chrome doesn't go through the
component to get back to its own whispernet client. Instead, keep a pointer to
the whispernet client in the chrome copresence delegate, or add some
FromBrowserContext() method to whispernet client.

the rest of the component lgtm

[rkc, 2014/07/31 15:44:13]

So I thought a bit more about this and realized that since we have only one
copresence_private API, we will never really be able to have more than one
WhispernetClient active at one time anyway.

Moved the WhispernetClient pointer to the delegate. The ownership of the
whispernet_client now lies with the copresence_client_delegate.

+  CopresenceClient(CopresenceClientDelegate* delegate,
+                   scoped_ptr<WhispernetClient> whispernet_client);
+  virtual ~CopresenceClient();
+
+  WhispernetClient* whispernet_client();
+
+  // This method will execute a report request. Each report request can have
+  // multiple (un)publishes, (un)subscribes. This will ensure that once the
+  // client is initialized, it sends all request to the server and handles
+  // the response. If an error is encountered, the status callback is used
+  // to relay it to the requester.
+  void ExecuteReportRequest(copresence::ReportRequest request,
+                            const std::string& app_id,
+                            const StatusCallback& callback);
+
+  // Called before the API (and thus the Client) is destructed.
+  void Shutdown();
+
+ private:
+  void CompleteInitialization();
+  void InitStepComplete(const std::string& step, bool success);
+
+  bool init_failed_;
+  std::vector<PendingRequest> pending_requests_queue_;
+
+  // TODO(rkc): This code is almost identical to what we use in feedback to
+  // perform multiple blocking tasks and then run a post process method. Look
+  // into refactoring it all out to a common construct, like maybe a
+  // PostMultipleTasksAndReply?
+  size_t pending_init_operations_;
+
+  scoped_ptr<WhispernetClient> whispernet_client_;
+  scoped_ptr<RpcHandler> rpc_handler_;
+
+  DISALLOW_COPY_AND_ASSIGN(CopresenceClient);
+};
+
+}  // namespace copresence
+
+#endif  // COMPONENTS_COPRESENCE_PUBLIC_COPRESENCE_CLIENT_H_