Log predictor database size on startup

chrome/browser/net/predictor.cc

Index: chrome/browser/net/predictor.cc
diff --git a/chrome/browser/net/predictor.cc b/chrome/browser/net/predictor.cc
index e375df45c21697a1cf163a67ddbea5c0ee2f9b55..7dd51e3d1991304a1140b313254be985ef22c609 100644
--- a/chrome/browser/net/predictor.cc
+++ b/chrome/browser/net/predictor.cc
@@ -672,6 +672,8 @@ void Predictor::FinalizeInitializationOnIOThread(
   DnsPrefetchMotivatedList(startup_urls, UrlInfo::STARTUP_LIST_MOTIVATED);
 
   DeserializeReferrersThenDelete(referral_list);
+
+  LogStartupMetrics();
 }
 
 //-----------------------------------------------------------------------------
@@ -1172,6 +1174,20 @@ GURL Predictor::GetHSTSRedirectOnIOThread(const GURL& url) {
   return url.ReplaceComponents(replacements);
 }
 
+void Predictor::LogStartupMetrics() {
+  size_t total_bytes = 0;
+  for (const auto& referrer : referrers_) {
+    total_bytes += referrer.first.spec().size();

[mmenke, 2016/06/20 17:01:24]

Could optionally add in in sizeof(ReferrerValue) here.

[Charlie Harrison, 2016/06/20 17:26:37]

Isn't that what sizeof(subresource.second) is doing below? Updated the code to
be a bit clear and added sizeof(Referrer) as well.

[mmenke, 2016/06/20 17:33:52]

Sorry, I meant sizeof(Referrer).  I find the object names here completely
unintuitive.  :(

[Charlie Harrison, 2016/06/20 17:35:13]

Agreed. Hoping to clean this up once we stop using Referer headers.

+    for (const auto& subresource: referrer.second) {

[mmenke, 2016/06/20 17:01:24]

nit:  Space before colon

[Charlie Harrison, 2016/06/20 17:26:37]

Done.

+      total_bytes += subresource.first.spec().size();
+      total_bytes += sizeof(subresource.second);
+    }
+  }
+  UMA_HISTOGRAM_CUSTOM_COUNTS("Net.Predictor.Startup.DBSize", total_bytes, 1,
+                              1000000000, 50);

[mmenke, 2016/06/20 17:01:24]

Suggest reducing this to 10 MB to get a finer breakdown.  Also, please write
this as X * 1000 * 1000, to make it easier to read.

[Charlie Harrison, 2016/06/20 17:26:37]

Done.

+}
+
+
 // ---------------------- End IO methods. -------------------------------------
 
 //-----------------------------------------------------------------------------