[PageLoadMetrics] Record bytes usage per page

chrome/browser/loader/chrome_resource_dispatcher_host_delegate.cc

Index: chrome/browser/loader/chrome_resource_dispatcher_host_delegate.cc
diff --git a/chrome/browser/loader/chrome_resource_dispatcher_host_delegate.cc b/chrome/browser/loader/chrome_resource_dispatcher_host_delegate.cc
index e5a36cc6d8ca2e66af63e593511b455b1402a60d..49eb5b180012c56725be9ff68bad5a1c85aaf9f7 100644
--- a/chrome/browser/loader/chrome_resource_dispatcher_host_delegate.cc
+++ b/chrome/browser/loader/chrome_resource_dispatcher_host_delegate.cc
@@ -359,6 +359,7 @@ void NotifyUIThreadOfRequestComplete(
     bool was_cached,
     int net_error,
     int64_t total_received_bytes,
+    int64_t raw_body_bytes,
     base::TimeDelta request_loading_time) {
   DCHECK_CURRENTLY_ON(content::BrowserThread::UI);
   content::WebContents* web_contents = web_contents_getter.Run();
@@ -374,7 +375,8 @@ void NotifyUIThreadOfRequestComplete(
       page_load_metrics::MetricsWebContentsObserver::FromWebContents(
           web_contents);
   if (metrics_observer) {
-    metrics_observer->OnRequestComplete(resource_type, was_cached, net_error);
+    metrics_observer->OnRequestComplete(resource_type, was_cached, net_error,
+                                        raw_body_bytes);
   }
 }
 
@@ -826,6 +828,7 @@ void ChromeResourceDispatcherHostDelegate::RequestComplete(
                  info->GetWebContentsGetterForRequest(), url_request->url(),
                  info->GetResourceType(), url_request->was_cached(), net_error,
                  url_request->GetTotalReceivedBytes(),
+                 url_request->GetRawBodyBytes(),

[RyanSturm, 2016/12/12 22:29:38]

I'm curious why you are using GetRawBodyBytes instead of GetTotalReceivedBytes.
Does it seem worth tracking GetTotalSentBytes as well? I'm not really sure what
exactly you are comparing and if bytes sent matters or if only bytes received
matter.

[jkarlin, 2016/12/19 19:26:01]

Right now only tracking received bytes. I'm using RawBodyBytes because I'm not
worried about how large the decoded resource is, I want to know how many network
and cache bytes the page load required.

We can always add decoded bytes and sent bytes later.

[RyanSturm, 2016/12/19 19:40:05]

I thought both of these tracked bytes after decoding SSL, but RawBodyBytes
doesn't include headers, I might be wrong on this though.
 

[jkarlin, 2016/12/20 14:03:58]

You're right that they both track bytes before decoding. The difference is that
the GetTotalReceivedBytes only counts bytes over the network while RawBodyBytes
counts body size regardless of if it came from the network or from cache. 

If we want the network and cached UMA values to be comparable, then they should
probably both use the same (body size). I could be persuaded otherwise though,
WDYT?

                  base::TimeTicks::Now() - url_request->creation_time()));
 }