Add metrics for calculating precision/recall of link navigation pre-connect triggers.

chrome/browser/renderer_host/chrome_render_message_filter.cc

Index: chrome/browser/renderer_host/chrome_render_message_filter.cc
diff --git a/chrome/browser/renderer_host/chrome_render_message_filter.cc b/chrome/browser/renderer_host/chrome_render_message_filter.cc
index 0fcde9643bbc32403f18be5db28fa7f14a7890af..413f343987866c1010d7998a46ca8d297b0965a2 100644
--- a/chrome/browser/renderer_host/chrome_render_message_filter.cc
+++ b/chrome/browser/renderer_host/chrome_render_message_filter.cc
@@ -335,8 +335,10 @@ void ChromeRenderMessageFilter::OnDnsPrefetch(
 }
 
 void ChromeRenderMessageFilter::OnPreconnect(const GURL& url) {
-  if (profile_->GetNetworkPredictor())
+  if (profile_->GetNetworkPredictor()) {
+    profile_->GetNetworkPredictor()->RecordPreconnectTrigger(url);

[cbentzel, 2013/06/24 01:46:46]

Could this move into PreconnectUrlAndSubresources? Why is it not being called in
the ChromeRenderViewHostObserver::Navigate case?

[kouhei (in TOK), 2013/06/24 05:51:09]

ChromeRenderViewHostObserver::Navigate seems to be called when a user types on
address bar. Our target is preconnect signals for link navigations.

     profile_->GetNetworkPredictor()->PreconnectUrlAndSubresources(url, GURL());
+  }
 }
 
 void ChromeRenderMessageFilter::OnResourceTypeStats(