[remoting-start-host] Fix crash in remoting::ServiceClient.

This adds an assignment that was removed in
http://crrev.com/f8c5470dd7bfe253825cce3272a1bbba913190dd

Bug: 901170
Change-Id: I43135804d2f0f6bee8ae3038cfc7682ccbfd7552
Reviewed-on: https://chromium-review.googlesource.com/c/1313337
Commit-Queue: Lambros Lambrou <lambroslambrou@chromium.org>
Commit-Queue: Joe Downing <joedow@chromium.org>
Reviewed-by: Joe Downing <joedow@chromium.org>
Cr-Commit-Position: refs/heads/master@{#604766}

remoting/host/setup/service_client.cc

@@ -100,6 +100,7 @@ void ServiceClient::Core::MakeChromotingRequest(
     const std::string& request_body,
     const std::string& oauth_access_token,
     ServiceClient::Delegate* delegate) {
+  delegate_ = delegate;
   auto resource_request = std::make_unique<network::ResourceRequest>();
   resource_request->url = GURL(chromoting_hosts_url_ + url_suffix);
   resource_request->method = request_type;