Fix socket send.

Instead of calling CopresenceSocket::Send with the size of the packet we
created, we were calling it with the size of the original data. This CL fixes
that bug and adds more logging when we're sending data.

R=xiyuan@chromium.org
BUG=None.

Review URL: https://codereview.chromium.org/698153005

Cr-Commit-Position: refs/heads/master@{#302656}

extensions/browser/api/copresence_socket/copresence_socket_api.cc

@@ -269,8 +269,14 @@ ExtensionFunction::ResponseAction CopresenceSocketSendFunction::Execute() {
             core_api::copresence_socket::SOCKET_STATUS_INVALID_SOCKET)));
   }
 
-  socket->socket()->Send(new net::StringIOBuffer(CreateMessage(params->data)),
-                         params->data.size());
+  const std::string& message = CreateMessage(params->data);
+  VLOG(3) << "Sending message to socket_id = " << params->socket_id
+          << " with data[0] = " << static_cast<int>(message[0])
+          << ", data[1] = " << static_cast<int>(message[1]) << ", data[2:] = "
+          << std::string((message.c_str() + 2), message.size() - 2);
+
+  socket->socket()->Send(new net::StringIOBuffer(message), message.size());
+
   return RespondNow(
       ArgumentList(core_api::copresence_socket::Send::Results::Create(
           core_api::copresence_socket::SOCKET_STATUS_NO_ERROR)));