Revise InterfaceRegistry API to support filtering interfaces @ Bind() time.

services/service_manager/public/cpp/lib/identity.cc

Index: services/service_manager/public/cpp/lib/identity.cc
diff --git a/services/service_manager/public/cpp/lib/identity.cc b/services/service_manager/public/cpp/lib/identity.cc
index 241b3f48e024a411abc6394878dc843634aa1505..99d9e17ee69f714134f516cf5d2574e0de505473 100644
--- a/services/service_manager/public/cpp/lib/identity.cc
+++ b/services/service_manager/public/cpp/lib/identity.cc
@@ -40,4 +40,8 @@ bool Identity::operator==(const Identity& other) const {
          other.user_id_ == user_id_;
 }
 
+bool Identity::IsValid() const {
+  return IsValidName(name_) && base::IsValidGUID(user_id_);
+}
+
 }  // namespace service_manager