buffet: Added unit tests for DeviceRegistrationInfo class

Added unit tests for GCD registration workflow in Buffet.

BUG=chromium:367381
TEST=Unit tests pass (old and new).

Change-Id: Ia3ad5f028ae6fc7f3d2acdf4648ceb88cc4e00ef
Reviewed-on: https://chromium-review.googlesource.com/197568
Tested-by: Alex Vakulenko <avakulenko@chromium.org>
Reviewed-by: Christopher Wiley <wiley@chromium.org>
Commit-Queue: Alex Vakulenko <avakulenko@chromium.org>
diff --git a/buffet/http_connection_fake.cc b/buffet/http_connection_fake.cc
index 0507c0b..6a1c3b9 100644
--- a/buffet/http_connection_fake.cc
+++ b/buffet/http_connection_fake.cc
@@ -40,6 +40,8 @@
   CHECK(transport) << "Expecting a fake transport";
   auto handler = transport->GetHandler(request_.GetURL(), request_.GetMethod());
   if (handler.is_null()) {
+    LOG(ERROR) << "Received unexpected " << request_.GetMethod()
+               << " request at " << request_.GetURL();
     response_.ReplyText(status_code::NotFound,
                         "<html><body>Not found</body></html>",
                         mime::text::kHtml);