Use std::string instead of mojo::String in //net.

net/proxy/in_process_mojo_proxy_resolver_factory.cc

 // Copyright 2015 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/in_process_mojo_proxy_resolver_factory.h"
 
 #include <utility>
 
 #include "base/memory/singleton.h"
 #include "mojo/public/cpp/bindings/strong_binding.h"
@@ skipping 10 matching lines @@
 InProcessMojoProxyResolverFactory::InProcessMojoProxyResolverFactory() {
   mojo::MakeStrongBinding(base::MakeUnique<MojoProxyResolverFactoryImpl>(),
                           mojo::GetProxy(&factory_));
 }
 
 InProcessMojoProxyResolverFactory::~InProcessMojoProxyResolverFactory() =
     default;
 
 std::unique_ptr<base::ScopedClosureRunner>
 InProcessMojoProxyResolverFactory::CreateResolver(
-    const mojo::String& pac_script,
+    const std::string& pac_script,
     mojo::InterfaceRequest<interfaces::ProxyResolver> req,
     interfaces::ProxyResolverFactoryRequestClientPtr client) {
   factory_->CreateResolver(pac_script, std::move(req), std::move(client));
   return nullptr;
 }
 
 }  // namespace net