Avoid doing concurrent DNS resolves of the same hostname

net/proxy/proxy_resolver_v8.h

Index: net/proxy/proxy_resolver_v8.h
===================================================================
--- net/proxy/proxy_resolver_v8.h	(revision 18213)
+++ net/proxy/proxy_resolver_v8.h	(working copy)
@@ -10,8 +10,12 @@
 #include "base/scoped_ptr.h"
 #include "net/proxy/proxy_resolver.h"
 
+class MessageLoop;
+
 namespace net {
 
+class HostResolver;
+
 // Implementation of ProxyResolver that uses V8 to evaluate PAC scripts.
 //
 // ----------------------------------------------------------------------------
@@ -32,19 +36,6 @@
 // and does not use locking since it expects to be alone.
 class ProxyResolverV8 : public ProxyResolver {
  public:
-  // Constructs a ProxyResolverV8 with default javascript bindings.
-  //
-  // The default javascript bindings will:
-  //   - Send script error messages to LOG(INFO)
-  //   - Send script alert()s to LOG(INFO)
-  //   - Use the default host mapper to service dnsResolve(), synchronously
-  //     on the V8 thread.
-  //
-  // For clients that need more control (for example, sending the script output
-  // to a UI widget), use the ProxyResolverV8(JSBindings*) and specify your
-  // own bindings.
-  ProxyResolverV8();
-
   class JSBindings;
 
   // Constructs a ProxyResolverV8 with custom bindings. ProxyResolverV8 takes
@@ -62,6 +53,21 @@
 
   JSBindings* js_bindings() const { return js_bindings_.get(); }
 
+  // Creates a default javascript bindings implementation that will:
+  //   - Send script error messages to LOG(INFO)
+  //   - Send script alert()s to LOG(INFO)
+  //   - Use the provided host mapper to service dnsResolve().
+  //
+  // For clients that need more control (for example, sending the script output
+  // to a UI widget), use the ProxyResolverV8(JSBindings*) and specify your
+  // own bindings.
+  //
+  // |host_resolver| will be used in async mode on |host_resolver_loop|. If
+  // |host_resolver_loop| is NULL, then |host_resolver| will be used in sync
+  // mode on the PAC thread.
+  static JSBindings* CreateDefaultBindings(HostResolver* host_resolver,
+                                           MessageLoop* host_resolver_loop);
+
  private:
   // Context holds the Javascript state for the most recently loaded PAC
   // script. It corresponds with the data from the last call to