Don't clear the net predictors prefs on startup

chrome/browser/chrome_net_benchmarking_message_filter.cc

Index: chrome/browser/chrome_net_benchmarking_message_filter.cc
diff --git a/chrome/browser/chrome_net_benchmarking_message_filter.cc b/chrome/browser/chrome_net_benchmarking_message_filter.cc
index b95edb47744fc37d27f1bc8e3b94023892d9f32c..ef57cf85d7d71cfc8166bd924077254023f6f51a 100644
--- a/chrome/browser/chrome_net_benchmarking_message_filter.cc
+++ b/chrome/browser/chrome_net_benchmarking_message_filter.cc
@@ -60,6 +60,13 @@ bool ChromeNetBenchmarkingMessageFilter::OnMessageReceived(
   return handled;
 }
 
+void ChromeNetBenchmarkingMessageFilter::OverrideThreadForMessage(
+    const IPC::Message& message,
+    content::BrowserThread::ID* thread) {
+  if (message.type() == ChromeViewHostMsg_ClearPredictorCache::ID)
+    *thread = content::BrowserThread::UI;
+}
+
 void ChromeNetBenchmarkingMessageFilter::OnClearCache(IPC::Message* reply_msg) {
   // This function is disabled unless the user has enabled
   // benchmarking extensions.
@@ -126,13 +133,16 @@ void ChromeNetBenchmarkingMessageFilter::OnSetCacheMode(bool enabled) {
 void ChromeNetBenchmarkingMessageFilter::OnClearPredictorCache() {
   // This function is disabled unless the user has enabled
   // benchmarking extensions.
+  DCHECK_CURRENTLY_ON(content::BrowserThread::UI);
   if (!CheckBenchmarkingEnabled()) {
     NOTREACHED() << "Received unexpected benchmarking IPC";
     return;
   }
+  // TODO(623967): Ensure that the profile or predictor are not accessed after
+  // they have been shut down.
   chrome_browser_net::Predictor* predictor = profile_->GetNetworkPredictor();
   if (predictor)
-    predictor->DiscardAllResults();
+    predictor->DiscardAllResultsAndClearPrefsOnUIThread();
 }
 
 bool ChromeNetBenchmarkingMessageFilter::CheckBenchmarkingEnabled() const {