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

net/proxy/in_process_mojo_proxy_resolver_factory.h

 // 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.
 
 #ifndef NET_PROXY_IN_PROCESS_MOJO_PROXY_RESOLVER_FACTORY_H_
 #define NET_PROXY_IN_PROCESS_MOJO_PROXY_RESOLVER_FACTORY_H_
 
 #include "base/macros.h"
 #include "net/proxy/mojo_proxy_resolver_factory.h"
 
 namespace base {
 template <typename T>
 struct DefaultSingletonTraits;
 }
 
 namespace net {
 
 // Factory to connect to an in-process Mojo proxy resolver service.
 // NOTE: This is intended to be temporary for debugging purposes and will be
 // removed when we're confident with the out-of-process implementation.
 class InProcessMojoProxyResolverFactory : public MojoProxyResolverFactory {
  public:
   static InProcessMojoProxyResolverFactory* GetInstance();
 
   // Overridden from MojoProxyResolverFactory:
   std::unique_ptr<base::ScopedClosureRunner> CreateResolver(
-      const mojo::String& pac_script,
+      const std::string& pac_script,
       mojo::InterfaceRequest<interfaces::ProxyResolver> req,
       interfaces::ProxyResolverFactoryRequestClientPtr client) override;
 
  private:
   InProcessMojoProxyResolverFactory();
   ~InProcessMojoProxyResolverFactory() override;
   friend struct base::DefaultSingletonTraits<InProcessMojoProxyResolverFactory>;
 
   interfaces::ProxyResolverFactoryPtr factory_;
 
   DISALLOW_COPY_AND_ASSIGN(InProcessMojoProxyResolverFactory);
 };
 
 }  // namespace net
 
 #endif  // NET_PROXY_IN_PROCESS_MOJO_PROXY_RESOLVER_FACTORY_H_