Add field trial to extend prerender expiration to 5 minutes.

chrome/browser/prerender/prerender_manager.cc

Index: chrome/browser/prerender/prerender_manager.cc
diff --git a/chrome/browser/prerender/prerender_manager.cc b/chrome/browser/prerender/prerender_manager.cc
index 8ab48092a24afb4f487dce067f9f4e06d7d870df..4848b39ec35f535c8c96336883362aeef5744875 100644
--- a/chrome/browser/prerender/prerender_manager.cc
+++ b/chrome/browser/prerender/prerender_manager.cc
@@ -415,7 +415,7 @@ bool PrerenderManager::MaybeUsePrerenderedPage(WebContents* web_contents,
   if (!prerender_contents->load_start_time().is_null()) {
     histograms_->RecordTimeUntilUsed(GetCurrentTimeTicks() -
                                      prerender_contents->load_start_time(),
-                                     config_.max_age);
+                                     GetMaxAge());
   }
 
   histograms_->RecordPerSessionCount(++prerenders_per_session_count_);
@@ -728,6 +728,8 @@ DictionaryValue* PrerenderManager::GetAsValue() const {
     dict_value->SetString("disabled_reason", "(Disabled for testing)");
   if (IsNoUseGroup())
     dict_value->SetString("disabled_reason", "(Not using prerendered pages)");
+  if (GetMode() == PRERENDER_MODE_EXPERIMENT_LONG_TTL_GROUP)
+    dict_value->SetString("disabled_reason", "(Long TTL)");

[cbentzel, 2012/02/28 00:53:41]

Perhaps "disabled_reason" should change names?

[dominich, 2012/02/28 17:51:31]

Done.

   return dict_value;
 }
 
@@ -984,10 +986,17 @@ void PrerenderManager::PostCleanupTask() {
                  weak_factory_.GetWeakPtr()));
 }
 
+base::TimeDelta PrerenderManager::GetMaxAge() const {
+  base::TimeDelta max_age = config_.max_age;
+  if (GetMode() == PRERENDER_MODE_EXPERIMENT_LONG_TTL_GROUP)
+    max_age *= 10;

[cbentzel, 2012/02/28 00:53:41]

Should this be constant rather than ratio?

[dominich, 2012/02/28 17:51:31]

Done.

+  return max_age;
+}
+
 bool PrerenderManager::IsPrerenderElementFresh(const base::Time start) const {
   DCHECK(CalledOnValidThread());
   base::Time now = GetCurrentTime();
-  return (now - start < config_.max_age);
+  return (now - start < GetMaxAge());
 }
 
 void PrerenderManager::DeleteOldEntries() {