Add ability to bind a different InterfaceRegistry/InterfaceProvider to an incoming Connection.

services/shell/public/cpp/lib/interface_provider.cc

 // Copyright 2016 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 "services/shell/public/cpp/interface_provider.h"
 
 namespace shell {
 
-InterfaceProvider::InterfaceProvider(
-    mojom::InterfaceProviderPtr interface_provider)
-    : interface_provider_(std::move(interface_provider)),
-      weak_factory_(this) {}
+InterfaceProvider::InterfaceProvider() : weak_factory_(this) {}
 InterfaceProvider::~InterfaceProvider() {}
 
+void InterfaceProvider::Bind(mojom::InterfaceProviderPtr interface_provider) {
+  DCHECK(!interface_provider_.is_bound());
+  interface_provider_ = std::move(interface_provider);
+}
+
 void InterfaceProvider::SetConnectionLostClosure(
     const base::Closure& connection_lost_closure) {
   interface_provider_.set_connection_error_handler(connection_lost_closure);
 }
 
 base::WeakPtr<InterfaceProvider> InterfaceProvider::GetWeakPtr() {
   return weak_factory_.GetWeakPtr();
 }
 
 void InterfaceProvider::GetInterface(
     const std::string& name,
     mojo::ScopedMessagePipeHandle request_handle) {
   // Local binders can be registered via TestApi.
   auto it = binders_.find(name);
   if (it != binders_.end()) {
     it->second.Run(std::move(request_handle));
     return;
   }
   interface_provider_->GetInterface(name, std::move(request_handle));
 }
 
 void InterfaceProvider::ClearBinders() {
   binders_.clear();
 }
 
 }  // namespace shell