Clean up dns prefetch code, and also port it.

- remove slave threads and use HostResolver in asynchronous mode instead (while still limiting number of concurrent lookups)

- make the implementation portable and make DnsMaster unit test compile and pass on Linux

- add more tests to DnsMaster unit test to simulate various shutdown scenarios, concurrent lookups, and to verify that we don't exceed our limit of concurrent lookup requests)

- remove some tests which relied on specifics of slaves' inner working

- adjust initialization and shutdown of dns prefetching (now it relies on the IO message loop being present)

Bonus: shutdown is almost instant now, no need to have a timeout.

BUG=5687, 6683

Review URL: http://codereview.chromium.org/15076

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@10021 0039d316-1c4b-4281-b951-d872f2087c98

1 files changed, 7 insertions, 8 deletions

diff --git a/chrome/browser/net/dns_global.cc b/chrome/browser/net/dns_global.cc
index 4e1f1a2..9733e52 100644
--- a/chrome/browser/net/dns_global.cc
+++ b/chrome/browser/net/dns_global.cc
@@ -382,7 +382,7 @@ void InitDnsPrefetch(PrefService* user_prefs) {
   const TimeDelta kAllowableShutdownTime(TimeDelta::FromSeconds(10));
   DCHECK(NULL == dns_master);
   if (!dns_master) {
-    dns_master = new DnsMaster(kAllowableShutdownTime);
+    dns_master = new DnsMaster();
     // We did the initialization, so we should prime the pump, and set up
     // the DNS resolution system to run.
     off_the_record_observer.Register();
@@ -401,14 +401,13 @@ void InitDnsPrefetch(PrefService* user_prefs) {
 
 void ShutdownDnsPrefetch() {
   DCHECK(NULL != dns_master);
-  DnsMaster* master = dns_master;
+  dns_master->Shutdown();
+}
+
+void FreeDnsPrefetchResources() {
+  DCHECK(NULL != dns_master);
+  delete dns_master;
   dns_master = NULL;
-  if (master->ShutdownSlaves()) {
-    delete master;
-  } else {
-    // Leak instance if shutdown problem.
-    DCHECK(0);
-  }
 }
 
 static void DiscardAllPrefetchState() {