Avoid doing concurrent DNS resolves of the same hostname

net/proxy/proxy_service.cc

 // Copyright (c) 2006-2008 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "net/proxy/proxy_service.h"
 
 #include <algorithm>
 
 #include "base/compiler_specific.h"
 #include "base/logging.h"
 #include "base/string_util.h"
 #include "googleurl/src/gurl.h"
 #include "net/base/net_errors.h"
 #include "net/proxy/proxy_config_service_fixed.h"
 #include "net/proxy/proxy_script_fetcher.h"
 #if defined(OS_WIN)
 #include "net/proxy/proxy_config_service_win.h"
 #include "net/proxy/proxy_resolver_winhttp.h"
 #elif defined(OS_MACOSX)
 #include "net/proxy/proxy_resolver_mac.h"
 #elif defined(OS_LINUX)
 #include "net/proxy/proxy_config_service_linux.h"
 #endif
 #include "net/proxy/proxy_resolver.h"
 #include "net/proxy/proxy_resolver_v8.h"
+#include "net/url_request/url_request_context.h"
 
 using base::TimeDelta;
 using base::TimeTicks;
 
 namespace net {
 
 // Config getter that fails every time.
 class ProxyConfigServiceNull : public ProxyConfigService {
  public:
   // ProxyConfigService implementation:
@@ skipping 174 matching lines @@
 ProxyService* ProxyService::Create(
     const ProxyConfig* pc,
     bool use_v8_resolver,
     URLRequestContext* url_request_context,
     MessageLoop* io_loop) {
   // Choose the system configuration service appropriate for each platform.
   ProxyConfigService* proxy_config_service = pc ?
       new ProxyConfigServiceFixed(*pc) :
       CreateSystemProxyConfigService(io_loop);
 
-  ProxyResolver* proxy_resolver = use_v8_resolver ?
-      new ProxyResolverV8() : CreateNonV8ProxyResolver();
+  ProxyResolver* proxy_resolver;
+
+  if (use_v8_resolver) {
+    // Send javascript errors and alerts to LOG(INFO).
+    HostResolver* host_resolver = url_request_context->host_resolver();
+    ProxyResolverV8::JSBindings* js_bindings =
+        ProxyResolverV8::CreateDefaultBindings(host_resolver, io_loop);
+
+    proxy_resolver = new ProxyResolverV8(js_bindings);
+  } else {
+    proxy_resolver = CreateNonV8ProxyResolver();
+  }
 
   ProxyService* proxy_service = new ProxyService(
       proxy_config_service, proxy_resolver);
 
   if (!proxy_resolver->does_fetch()) {
     // Configure PAC script downloads to be issued using |url_request_context|.
     DCHECK(url_request_context);
     proxy_service->SetProxyScriptFetcher(
         ProxyScriptFetcher::Create(url_request_context));
   }
@@ skipping 518 matching lines @@
     OnCompletion(result_);
   }
 }
 
 void SyncProxyServiceHelper::OnCompletion(int rv) {
   result_ = rv;
   event_.Signal();
 }
 
 }  // namespace net