Adds UMA to measure when the data reduction proxy via header is missing

chrome/browser/net/chrome_network_delegate.cc

Index: chrome/browser/net/chrome_network_delegate.cc
diff --git a/chrome/browser/net/chrome_network_delegate.cc b/chrome/browser/net/chrome_network_delegate.cc
index 285a2e31f620f92b7a0e0c2c1cb236c792be813a..a88c1b8a30088d99eea82c5bb860864132f383a8 100644
--- a/chrome/browser/net/chrome_network_delegate.cc
+++ b/chrome/browser/net/chrome_network_delegate.cc
@@ -586,9 +586,12 @@ void ChromeNetworkDelegate::OnCompleted(net::URLRequest* request,
       RecordContentLengthHistograms(received_content_length,
                                     original_content_length,
                                     freshness_lifetime);
+
       if (data_reduction_proxy_enabled_ &&
           data_reduction_proxy_usage_stats_ &&
           !proxy_config_getter_.is_null()) {
+        data_reduction_proxy_usage_stats_->RecordMissingViaHeaderBytes(request);

[mmenke, 2014/09/18 18:39:30]

This function name is very confusing, since it's always called, even when we
have a via header.  Also seems weird that this takes request and the next takes
*request.

I think to keep things simplest, you should just merge them into
DataReductionProxyUsageStats::RecordByteHistograms(*request,
*data_decution_proxy_enable_, proxy_config_getter_.Run());

[sclittle, 2014/09/19 01:05:01]

Done.

+
         data_reduction_proxy_usage_stats_->RecordBypassedBytesHistograms(
             *request,
             *data_reduction_proxy_enabled_,