Improve web_proxy reliability

I was discovering some weird unreliability on my laptop. Not really sure
why, but for some reason we were sending WebRTC messages on the client
side and the browser just wasn't delivering them. Didn't triage that
carefully enough to be sure if that was browser side or server side.

Change-Id: Icb64d379abcaf1be3f0ae550fe09b8bce744275c
Signed-off-by: James Kuszmaul <jabukuszmaul+collab@gmail.com>
diff --git a/aos/network/web_proxy.h b/aos/network/web_proxy.h
index 5526d07..db7fb5b 100644
--- a/aos/network/web_proxy.h
+++ b/aos/network/web_proxy.h
@@ -3,6 +3,7 @@
 
 #include <deque>
 #include <map>
+#include <optional>
 #include <set>
 
 #include "flatbuffers/flatbuffers.h"
@@ -156,6 +157,7 @@
     // The last queue/packet index reported by the client.
     uint32_t reported_queue_index = 0;
     size_t reported_packet_index = 0;
+    std::optional<aos::monotonic_clock::time_point> last_report = std::nullopt;
   };
   struct Message {
     uint32_t index = 0xffffffff;