Don't clear the net predictors prefs 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 44921f8b1658bf657309a3cc3155082d1df86460..4e6073cdba9bdefb9eba4f3f19017ccd7965c486 100644
--- a/chrome/browser/net/predictor.cc
+++ b/chrome/browser/net/predictor.cc
@@ -146,16 +146,8 @@ void Predictor::InitNetworkPredictor(PrefService* user_prefs,
   // Gather the list of hostnames to prefetch on startup.
   std::vector<GURL> urls = GetPredictedUrlListAtStartup(user_prefs);
 
-  base::ListValue* referral_list =
-      static_cast<base::ListValue*>(user_prefs->GetList(
-          prefs::kDnsPrefetchingHostReferralList)->DeepCopy());
-
-  // Now that we have the statistics in memory, wipe them from the Preferences
-  // file. They will be serialized back on a clean shutdown. This way we only
-  // have to worry about clearing our in-memory state when Clearing Browsing

[eroman, 2016/06/25 01:12:53]

(Not familiar with this previous code, but the previous design seems a bit odd
if this was the only motivation)

[Charlie Harrison, 2016/06/27 18:57:12]

Yeah this was my impression as well. It makes some sense considering some of the
complications here (i.e. having to jump to the UI thread to ensure deletion).
But still, I think this is saner.

-  // Data.
-  user_prefs->ClearPref(prefs::kDnsPrefetchingStartupList);
-  user_prefs->ClearPref(prefs::kDnsPrefetchingHostReferralList);
+  const base::ListValue* referral_list =
+      user_prefs->GetList(prefs::kDnsPrefetchingHostReferralList);
 
   BrowserThread::PostTask(
       BrowserThread::IO,
@@ -574,12 +566,6 @@ void Predictor::DeserializeReferrers(const base::ListValue& referral_list) {
   }
 }
 
-void Predictor::DeserializeReferrersThenDelete(
-    base::ListValue* referral_list) {
-  DeserializeReferrers(*referral_list);
-  delete referral_list;
-}
-
 void Predictor::DiscardInitialNavigationHistory() {
   DCHECK_CURRENTLY_ON(BrowserThread::IO);
   if (initial_observer_.get())
@@ -588,7 +574,7 @@ void Predictor::DiscardInitialNavigationHistory() {
 
 void Predictor::FinalizeInitializationOnIOThread(
     const std::vector<GURL>& startup_urls,
-    base::ListValue* referral_list,
+    const base::ListValue* referral_list,
     IOThread* io_thread,
     ProfileIOData* profile_io_data) {
   DCHECK_CURRENTLY_ON(BrowserThread::IO);
@@ -612,7 +598,7 @@ void Predictor::FinalizeInitializationOnIOThread(
   // Prefetch these hostnames on startup.
   DnsPrefetchMotivatedList(startup_urls, UrlInfo::STARTUP_LIST_MOTIVATED);
 
-  DeserializeReferrersThenDelete(referral_list);
+  DeserializeReferrers(*referral_list);
 
   LogStartupMetrics();
 }
@@ -849,6 +835,20 @@ bool Predictor::CanPreresolveAndPreconnect() const {
   }
 }
 
+void Predictor::ClearPrefsOnUIThread() {
+  DCHECK_CURRENTLY_ON(BrowserThread::UI);
+  user_prefs_->ClearPref(prefs::kDnsPrefetchingStartupList);
+  user_prefs_->ClearPref(prefs::kDnsPrefetchingHostReferralList);
+}
+
+void Predictor::DiscardAllResultAndClearPrefs() {
+  DCHECK_CURRENTLY_ON(BrowserThread::IO);
+  DiscardAllResults();
+  BrowserThread::PostTask(BrowserThread::UI, FROM_HERE,
+                          base::Bind(&Predictor::ClearPrefsOnUIThread,
+                                     weak_factory_->GetWeakPtr()));
+}
+
 enum SubresourceValue {
   PRECONNECTION,
   PRERESOLUTION,