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

services/shell/public/cpp/interface_provider.h

Index: services/shell/public/cpp/interface_provider.h
diff --git a/services/shell/public/cpp/interface_provider.h b/services/shell/public/cpp/interface_provider.h
index ccbfbb060fd3502ba5b626a3c19ba35f415b56d0..9924bc068229798cae3a1b9a58e6d597a9ac87e5 100644
--- a/services/shell/public/cpp/interface_provider.h
+++ b/services/shell/public/cpp/interface_provider.h
@@ -38,9 +38,11 @@ class InterfaceProvider {
     DISALLOW_COPY_AND_ASSIGN(TestApi);
   };
 
-  explicit InterfaceProvider(mojom::InterfaceProviderPtr interface_provider);
+  InterfaceProvider();
   ~InterfaceProvider();
 
+  void Bind(mojom::InterfaceProviderPtr interface_provider);
+
   // Returns a raw pointer to the remote InterfaceProvider.
   mojom::InterfaceProvider* get() { return interface_provider_.get(); }