Add audible support to the copresence API.

components/copresence/rpc/http_post.h

Index: components/copresence/rpc/http_post.h
diff --git a/components/copresence/rpc/http_post.h b/components/copresence/rpc/http_post.h
index 5de67f2d0ce8c75dfea22246d51a47fbba3ba5d5..d3c70a51f2a63fa7682807fa357506703a332fb8 100644
--- a/components/copresence/rpc/http_post.h
+++ b/components/copresence/rpc/http_post.h
@@ -32,9 +32,8 @@ namespace copresence {
 class HttpPost : public net::URLFetcherDelegate {
  public:
   // Callback to receive the HTTP status code and body of the response
-  // (if any). A pointer to this HttpPost object is also passed along.
-  typedef base::Callback<void(int, const std::string&, HttpPost*)>
-      ResponseCallback;
+  // (if any).
+  typedef base::Callback<void(int, const std::string&)> ResponseCallback;
 
   // An id for testing url fetching.
   static const int kUrlFetcherId = 1;
@@ -46,8 +45,9 @@ class HttpPost : public net::URLFetcherDelegate {
   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);
+           const google::protobuf::MessageLite& request_proto);
+
+  void Start(const ResponseCallback& response_callback);
 
   // HTTP requests are cancelled on delete.
   virtual ~HttpPost();