Revert "Clean up dns prefetch code, and also port it."

chrome/browser/net/dns_global.cc

Index: chrome/browser/net/dns_global.cc
diff --git a/chrome/browser/net/dns_global.cc b/chrome/browser/net/dns_global.cc
index 2f85b5912053e084a825b816efad2fb4feecd753..b34de8a3b4859398feafa70b4dc99f64e5df95bc 100644
--- a/chrome/browser/net/dns_global.cc
+++ b/chrome/browser/net/dns_global.cc
@@ -377,9 +377,13 @@ void DnsPrefetchGetHtmlInfo(std::string* output) {
 static PrefetchObserver dns_resolution_observer;
 
 void InitDnsPrefetch(PrefService* user_prefs) {
+  // Use a large shutdown time so that UI tests (that instigate lookups, and
+  // then try to shutdown the browser) don't instigate the CHECK about
+  // "some slaves have not finished"
+  const TimeDelta kAllowableShutdownTime(TimeDelta::FromSeconds(10));
   DCHECK(NULL == dns_master);
   if (!dns_master) {
-    dns_master = new DnsMaster();
+    dns_master = new DnsMaster(kAllowableShutdownTime);
     // We did the initialization, so we should prime the pump, and set up
     // the DNS resolution system to run.
     off_the_record_observer.Register();
@@ -398,8 +402,14 @@ void InitDnsPrefetch(PrefService* user_prefs) {
 
 void ShutdownDnsPrefetch() {
   DCHECK(NULL != dns_master);
-  delete dns_master;
+  DnsMaster* master = dns_master;
   dns_master = NULL;
+  if (master->ShutdownSlaves()) {
+    delete master;
+  } else {
+    // Leak instance if shutdown problem.
+    DCHECK(0);
+  }
 }
 
 static void DiscardAllPrefetchState() {