Mojo: Use InterfaceFactory<Interface> for service registration

mojo/public/cpp/bindings/interface_impl.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_BINDINGS_INTERFACE_IMPL_H_
 #define MOJO_PUBLIC_CPP_BINDINGS_INTERFACE_IMPL_H_
 
 #include "mojo/public/cpp/bindings/interface_request.h"
 #include "mojo/public/cpp/bindings/lib/interface_impl_internal.h"
 #include "mojo/public/cpp/environment/environment.h"
@@ skipping 37 matching lines @@
   // DO NOT USE. Exposed only for internal use and for testing.
   internal::InterfaceImplState<Interface>* internal_state() {
     return &internal_state_;
   }
 
  private:
   internal::InterfaceImplState<Interface> internal_state_;
   MOJO_DISALLOW_COPY_AND_ASSIGN(InterfaceImpl);
 };
 
+// Use InterfaceImplDeleteOnError if your interface implementation should delete
+// itself when detecting a connection error.
+template <typename Interface>
+class InterfaceImplDeleteOnError : public InterfaceImpl<Interface> {
+ public:
+  virtual ~InterfaceImplDeleteOnError() {}
+  virtual void OnConnectionError() { delete this; }

[tim (not reviewing), 2014/07/11 01:33:41]

I might be missing something, but I think one thing this changes from the
ServiceConnection method is that it's easy to break the
InterfaceImplDeleteOnError behavior if the implementation overrides
OnConnectionError and forgets to call the super version.. right?   With
ServiceConnection that (somewhat subtly) wouldn't happen, because
ServiceConnection was the bottom of the chain.

[darin (slow to review), 2014/07/11 03:52:35]

A template arg to InterfaceImpl<> would help solve this issue. InterfaceImplBase
could then implement the "delete on error" policy.

class FooImpl : public InterfaceImpl<Foo, DeleteOnError> {...};

+};
+
 // Takes an instance of an InterfaceImpl<..> subclass and binds it to the given
 // MessagePipe. The instance is returned for convenience in member initializer
 // lists, etc. If the pipe is closed, the instance's OnConnectionError method
 // will be called.
 //
 // The instance is also bound to the current thread. Its methods will only be
 // called on the current thread, and if the current thread exits, then it will
 // also be deleted, and along with it, its end point of the pipe will be closed.
 //
 // Before returning, the instance's OnConnectionEstablished method is called.
@@ skipping 40 matching lines @@
 Impl* BindToRequest(
     Impl* instance,
     InterfaceRequest<Interface>* request,
     const MojoAsyncWaiter* waiter = Environment::GetDefaultAsyncWaiter()) {
   return BindToPipe(instance, request->PassMessagePipe(), waiter);
 }
 
 }  // namespace mojo
 
 #endif  // MOJO_PUBLIC_CPP_BINDINGS_INTERFACE_IMPL_H_