Expose NavigatorHost via Embed() rather than globally.

mojo/public/cpp/application/lazy_interface_ptr.h

 // Copyright 2014 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 MOJO_PUBLIC_CPP_APPLICATION_LAZY_INTERFACE_PTR_H_
 #define MOJO_PUBLIC_CPP_APPLICATION_LAZY_INTERFACE_PTR_H_
 
 #include <string>
 
 #include "mojo/public/cpp/application/connect.h"
 #include "mojo/public/interfaces/application/service_provider.mojom.h"
 
 namespace mojo {
 
 template<typename Interface>
-class LazyInterfacePtr : InterfacePtr<Interface> {
+class LazyInterfacePtr : public InterfacePtr<Interface> {
  public:
+  LazyInterfacePtr() : service_provider_(NULL) {}
+
   LazyInterfacePtr(ServiceProvider* service_provider)
       : service_provider_(service_provider) {
   }
 
+  void set_service_provider(ServiceProvider* service_provider) {
+    if (service_provider != service_provider_) {
+      InterfacePtr<Interface>::reset();
+    }
+    service_provider_ = service_provider;
+  }
+
   Interface* get() const {
     if (!InterfacePtr<Interface>::get()) {
       mojo::ConnectToService<Interface>(
           service_provider_,
           const_cast<LazyInterfacePtr<Interface>*>(this));
     }
     return InterfacePtr<Interface>::get();
   }
   Interface* operator->() const { return get(); }
   Interface& operator*() const { return *get(); }
 
  private:
   ServiceProvider* service_provider_;
 };
 
 }  // namespace mojo
 
 #endif  // MOJO_PUBLIC_CPP_APPLICATION_LAZY_INTERFACE_PTR_H_