* Avoid doing concurrent DNS resolves of the same hostname in HostResolver.

* Add a 1 minute cache for host resolves.

* Refactor HostResolver to handle multiple requests.

* Make HostResolver a dependency of URLRequestContext. operate the HostResolver
in async mode for proxy resolver (bridging to IO thread).

TEST=unittests
BUG=13163

Review URL: http://codereview.chromium.org/118100

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@18236 0039d316-1c4b-4281-b951-d872f2087c98

4 files changed, 26 insertions, 17 deletions

diff --git a/chrome/browser/net/chrome_url_request_context.cc b/chrome/browser/net/chrome_url_request_context.cc
index 0a1fb13..b188694 100644
--- a/chrome/browser/net/chrome_url_request_context.cc
+++ b/chrome/browser/net/chrome_url_request_context.cc
@@ -10,6 +10,7 @@
 #include "chrome/browser/chrome_thread.h"
 #include "chrome/browser/extensions/extensions_service.h"
 #include "chrome/browser/extensions/user_script_master.h"
+#include "chrome/browser/net/dns_global.h"
 #include "chrome/browser/profile.h"
 #include "chrome/common/chrome_constants.h"
 #include "chrome/common/chrome_switches.h"
@@ -109,11 +110,15 @@ ChromeURLRequestContext* ChromeURLRequestContext::CreateOriginal(
   DCHECK(!profile->IsOffTheRecord());
   ChromeURLRequestContext* context = new ChromeURLRequestContext(profile);
 
+  // Global host resolver for the context.
+  context->host_resolver_ = chrome_browser_net::GetGlobalHostResolver();
+
   context->proxy_service_ = CreateProxyService(
       context, *CommandLine::ForCurrentProcess());
 
   net::HttpCache* cache =
-      new net::HttpCache(context->proxy_service_,
+      new net::HttpCache(context->host_resolver_,
+                         context->proxy_service_,
                          disk_cache_path.ToWStringHack(), 0);
 
   const CommandLine& command_line = *CommandLine::ForCurrentProcess();
@@ -133,9 +138,11 @@ ChromeURLRequestContext* ChromeURLRequestContext::CreateOriginal(
   // implementations on Windows.
 #if defined(OS_WIN)
   if (command_line.HasSwitch(switches::kNewFtp))
-    context->ftp_transaction_factory_ = new net::FtpNetworkLayer;
+    context->ftp_transaction_factory_ =
+        new net::FtpNetworkLayer(context->host_resolver_);
 #else
-  context->ftp_transaction_factory_ = new net::FtpNetworkLayer;
+  context->ftp_transaction_factory_ =
+      new net::FtpNetworkLayer(context->host_resolver_);
 #endif
 
   // setup cookie store
@@ -183,14 +190,16 @@ ChromeURLRequestContext* ChromeURLRequestContext::CreateOffTheRecord(
   DCHECK(profile->IsOffTheRecord());
   ChromeURLRequestContext* context = new ChromeURLRequestContext(profile);
 
-  // Share the same proxy service as the original profile. This proxy
-  // service's lifespan is dependent on the lifespan of the original profile,
-  // which we reference (see above).
+  // Share the same proxy service and host resolver as the original profile.
+  // This proxy service's lifespan is dependent on the lifespan of the original
+  // profile which we reference (see above).
+  context->host_resolver_ =
+      profile->GetOriginalProfile()->GetRequestContext()->host_resolver();
   context->proxy_service_ =
       profile->GetOriginalProfile()->GetRequestContext()->proxy_service();
 
   context->http_transaction_factory_ =
-      new net::HttpCache(context->proxy_service_, 0);
+      new net::HttpCache(context->host_resolver_, context->proxy_service_, 0);
   context->cookie_store_ = new net::CookieMonster;
 
   return context;
@@ -241,7 +250,8 @@ ChromeURLRequestContext* ChromeURLRequestContext::CreateRequestContextForMedia(
   } else {
     // If original HttpCache doesn't exist, simply construct one with a whole
     // new set of network stack.
-    cache = new net::HttpCache(original_context->proxy_service(),
+    cache = new net::HttpCache(original_context->host_resolver(),
+                               original_context->proxy_service(),
                                disk_cache_path.ToWStringHack(), 0);
   }
 
@@ -417,4 +427,7 @@ ChromeURLRequestContext::~ChromeURLRequestContext() {
   // it is owned by the original URLRequestContext.
   if (!is_off_the_record_ && !is_media_)
     delete proxy_service_;
+
+  // Do not delete host_resolver_; it will be freed by FreeGlobalHostResolver()
+  // during the teardown of DNS prefetching.
 }
diff --git a/chrome/browser/net/dns_global.cc b/chrome/browser/net/dns_global.cc
index 5aaa471..c54b14d 100644
--- a/chrome/browser/net/dns_global.cc
+++ b/chrome/browser/net/dns_global.cc
@@ -429,14 +429,11 @@ static net::HostResolver* global_host_resolver = NULL;
 net::HostResolver* GetGlobalHostResolver() {
   // Called from UI thread.
   if (!global_host_resolver) {
-  // TODO(eroman):
-#if 0
     static const size_t kMaxHostCacheEntries = 100;
     static const size_t kHostCacheExpirationSeconds = 60;  // 1 minute.
 
     global_host_resolver = new net::HostResolver(
         kMaxHostCacheEntries, kHostCacheExpirationSeconds * 1000);
-#endif
   }
   return global_host_resolver;
 }
@@ -444,8 +441,6 @@ net::HostResolver* GetGlobalHostResolver() {
 void FreeGlobalHostResolver() {
   if (global_host_resolver) {
     // Called from IO thread.
-    DCHECK_EQ(MessageLoop::current(),
-              g_browser_process->io_thread()->message_loop());
     delete global_host_resolver;
     global_host_resolver = NULL;
   }
diff --git a/chrome/browser/net/dns_master.cc b/chrome/browser/net/dns_master.cc
index 0477ddb..6151087 100644
--- a/chrome/browser/net/dns_master.cc
+++ b/chrome/browser/net/dns_master.cc
@@ -25,12 +25,13 @@ namespace chrome_browser_net {
 class DnsMaster::LookupRequest {
  public:
   LookupRequest(DnsMaster* master,
-                net::HostResolver* /*host_resolver*/,
+                net::HostResolver* host_resolver,
                 const std::string& hostname)
       : ALLOW_THIS_IN_INITIALIZER_LIST(
           net_callback_(this, &LookupRequest::OnLookupFinished)),
         master_(master),
-        hostname_(hostname) {
+        hostname_(hostname),
+        resolver_(host_resolver) {
   }
 
   bool Start() {
@@ -50,7 +51,7 @@ class DnsMaster::LookupRequest {
   DnsMaster* master_;  // Master which started us.
 
   const std::string hostname_;  // Hostname to resolve.
-  net::HostResolver resolver_;
+  net::SingleRequestHostResolver resolver_;
   net::AddressList addresses_;
 
   DISALLOW_COPY_AND_ASSIGN(LookupRequest);
diff --git a/chrome/browser/net/dns_master_unittest.cc b/chrome/browser/net/dns_master_unittest.cc
index debc943..be68dfb 100644
--- a/chrome/browser/net/dns_master_unittest.cc
+++ b/chrome/browser/net/dns_master_unittest.cc
@@ -113,7 +113,7 @@ TimeDelta BlockingDnsLookup(const std::string& hostname) {
 
     net::HostResolver resolver;
     net::AddressList addresses;
-    resolver.Resolve(hostname, 80, &addresses, NULL);
+    resolver.Resolve(hostname, 80, &addresses, NULL, NULL);
 
     return Time::Now() - start;
 }