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, 6 insertions, 0 deletions

diff --git a/chrome/browser/browser_process_impl.cc b/chrome/browser/browser_process_impl.cc
index eb545e5..21bd96b 100644
--- a/chrome/browser/browser_process_impl.cc
+++ b/chrome/browser/browser_process_impl.cc
@@ -14,6 +14,7 @@
 #include "chrome/browser/download/save_file_manager.h"
 #include "chrome/browser/google_url_tracker.h"
 #include "chrome/browser/metrics/metrics_service.h"
+#include "chrome/browser/net/dns_global.h"
 #include "chrome/browser/profile_manager.h"
 #include "chrome/browser/renderer_host/render_process_host.h"
 #include "chrome/browser/renderer_host/resource_dispatcher_host.h"
@@ -174,6 +175,11 @@ BrowserProcessImpl::~BrowserProcessImpl() {
     resource_dispatcher_host()->Shutdown();
   }
 
+  // Shutdown DNS prefetching now to ensure that network stack objects
+  // living on the IO thread get destroyed before the IO thread goes away.
+  io_thread_->message_loop()->PostTask(FROM_HERE,
+      NewRunnableFunction(chrome_browser_net::ShutdownDnsPrefetch));
+
   // Need to stop io_thread_ before resource_dispatcher_host_, since
   // io_thread_ may still deref ResourceDispatcherHost and handle resource
   // request before going away.