Adding the Copresence RpcHandler and HttpPost helper.

components/copresence/rpc/http_post.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_RPC_HTTP_POST_H_
+#define COMPONENTS_COPRESENCE_RPC_HTTP_POST_H_
+
+#include <string>
+
+#include "base/callback.h"
+#include "base/macros.h"
+#include "base/memory/scoped_ptr.h"
+#include "base/memory/weak_ptr.h"
+#include "net/url_request/url_fetcher_delegate.h"
+
+namespace google {
+namespace protobuf {
+class MessageLite;
+}
+}
+
+namespace net {
+class URLRequestContextGetter;
+}
+
+namespace copresence {
+
+// This class handles all Apiary calls to the Copresence server.
+// It configures the HTTP request appropriately and reports any errors.
+// Clients should not attempt to delete this class, as it needs to
+// persist until the HTTP request completes (or times out).
+//
+// TODO(ckehoe): Add retry logic.
+// TODO(ckehoe): Template this class to parse the proto received.

[Daniel Erat, 2014/08/06 21:35:18]

it'd probably be better to avoid templates if possible here, since i believe
they e.g. require defining this class in a header

[Charlie, 2014/08/06 22:36:23]

Can you clarify the cost of moving the implementation to a header? What's at
stake besides a millisecond or two of compile time?

[Daniel Erat, 2014/08/06 22:45:08]

- bigger binaries since the implementation is being duplicated in callers
- hard-to-read interface

in general, i think that there's a push in chromium to avoid templates except in
cases where you're writing general code that needs to be able to operate on
arbitrary types.

[Charlie, 2014/08/06 23:30:25]

Makes sense. You mean the implementation is duplicated per set of template
parameters, right? I hope the compiler/linker dedupes vector<int>, for example,
instead of keeping one copy per .o file.

Actually this need may go away, since we're talking about getting rid of the
RegisterDevice rpc.

+class HttpPost : public net::URLFetcherDelegate,
+                 public base::SupportsWeakPtr<HttpPost> {
+ public:
+  // Callback to receive the HTTP status code and body of the response (if any).
+  typedef base::Callback<void(int, const std::string&)> ResponseCallback;
+
+  // An id for testing url fetching.
+  static const int kUrlFetcherId = 1;
+
+  // Send a request to the Copresence server. After calling the callback, this
+  // object will delete itself. |url_context_getter| is owned by the caller,
+  // and must be valid until the request is actually sent (on the IO thread).
+  HttpPost(net::URLRequestContextGetter* url_context_getter,
+           const std::string& server_host,
+           const std::string& rpc_name,
+           const google::protobuf::MessageLite& request_proto,
+           const ResponseCallback& response_callback);
+
+ private:
+  // This class deletes itself when the request completes (or times out).
+  virtual ~HttpPost();
+
+  // Overridden from net::URLFetcherDelegate.
+  virtual void OnURLFetchComplete(const net::URLFetcher* source) OVERRIDE;
+
+  ResponseCallback response_callback_;
+  scoped_ptr<net::URLFetcher> url_fetcher_;
+
+  DISALLOW_COPY_AND_ASSIGN(HttpPost);
+};
+
+}  // namespace copresence
+
+#endif  // COMPONENTS_COPRESENCE_RPC_HTTP_POST_H_