Would you please add more context to explain what this issue is about? Thanks.

The Data Reduction Proxy uses a pingback mechanism to report page load times to the server for page loads that use the proxy server for the main request. These pingbacks are sent as low priority, and only one outstanding (i.e. already on the network) request exists at one time.  If multiple page loads report page load timing information while a pingback is on the network, those page load metrics can all be added to the same pingback request, so less bandwidth is used on pingback requests.

This landed, but the bot didn't generate the normal reponse; here's the CL: https://codereview.chromium.org/2155783002/