Mojo: Use InterfaceFactory<Interface> for service registration

mojo/public/cpp/bindings/interface_impl.h

Index: mojo/public/cpp/bindings/interface_impl.h
diff --git a/mojo/public/cpp/bindings/interface_impl.h b/mojo/public/cpp/bindings/interface_impl.h
index 4a78cb4b05a1f11b4380a001aab45fa76e91a8e2..387c62d0a41ec522c895738db2fbfd00325d3c40 100644
--- a/mojo/public/cpp/bindings/interface_impl.h
+++ b/mojo/public/cpp/bindings/interface_impl.h
@@ -55,6 +55,15 @@ class InterfaceImpl : public internal::InterfaceImplBase<Interface> {
   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