Split ProxyResolverV8Tracing into an implementation and a wrapper.

net/proxy/mojo_proxy_resolver_factory_impl_unittest.cc

Index: net/proxy/mojo_proxy_resolver_factory_impl_unittest.cc
diff --git a/net/proxy/mojo_proxy_resolver_factory_impl_unittest.cc b/net/proxy/mojo_proxy_resolver_factory_impl_unittest.cc
index fc1c94be9b48eb26a2aa22fd3fbb5567fa4050ed..a0d91808e413838661789fb4fe4f55bcb70da9c9 100644
--- a/net/proxy/mojo_proxy_resolver_factory_impl_unittest.cc
+++ b/net/proxy/mojo_proxy_resolver_factory_impl_unittest.cc
@@ -76,10 +76,8 @@ class MojoProxyResolverFactoryImplTest
 
   scoped_ptr<ProxyResolverFactory> CreateFakeProxyResolverFactory(
       HostResolver* host_resolver,
-      scoped_ptr<ProxyResolverErrorObserver> error_observer,
-      const ProxyResolver::LoadStateChangedCallback& callback) {
+      scoped_ptr<ProxyResolverErrorObserver> error_observer) {
     EXPECT_TRUE(host_resolver);
-    EXPECT_FALSE(callback.is_null());
     DCHECK(mock_factory_owner_);
     return mock_factory_owner_.Pass();
   }