Expose NavigatorHost via Embed() rather than globally.

mojo/public/cpp/application/lazy_interface_ptr.h

Index: mojo/public/cpp/application/lazy_interface_ptr.h
diff --git a/mojo/public/cpp/application/lazy_interface_ptr.h b/mojo/public/cpp/application/lazy_interface_ptr.h
index 62d0ae9f6ee32d414ec63ce69f9b4362b5dd682b..908ea0854b83ea12541fbfc9b37983f9bb1b6bb9 100644
--- a/mojo/public/cpp/application/lazy_interface_ptr.h
+++ b/mojo/public/cpp/application/lazy_interface_ptr.h
@@ -13,12 +13,21 @@
 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>(