Mojo C++ bindings: always use MultiplexRouter with InterfacePtr/Binding.

mojo/public/cpp/bindings/lib/interface_ptr_state.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_LIB_INTERFACE_PTR_STATE_H_
 #define MOJO_PUBLIC_CPP_BINDINGS_LIB_INTERFACE_PTR_STATE_H_
 
 #include <stdint.h>
 
 #include <algorithm>  // For |std::swap()|.
@@ skipping 327 matching lines @@
     // The proxy has been configured.
     if (proxy_) {
       DCHECK(router_);
       DCHECK(endpoint_client_);
       return;
     }
     // The object hasn't been bound.
     if (!handle_.is_valid())
       return;
 
-    router_ = new MultiplexRouter(
-        std::move(handle_), MultiplexRouter::MULTI_INTERFACE, true, runner_);
+    MultiplexRouter::Config config =
+        Interface::PassesAssociatedKinds_
+            ? MultiplexRouter::MULTI_INTERFACE
+            : (Interface::HasSyncMethods_
+                   ? MultiplexRouter::SINGLE_INTERFACE_WITH_SYNC_METHODS
+                   : MultiplexRouter::SINGLE_INTERFACE);
+    router_ = new MultiplexRouter(std::move(handle_), config, true, runner_);
     router_->SetMasterInterfaceName(Interface::Name_);
     endpoint_client_.reset(new InterfaceEndpointClient(
         router_->CreateLocalEndpointHandle(kMasterInterfaceId), nullptr,
         base::WrapUnique(new typename Interface::ResponseValidator_()), false,
         std::move(runner_),
         // The version is only queried from the client so the value passed here
         // will not be used.
         0u));
     proxy_.reset(new Proxy(endpoint_client_.get()));
     proxy_->serialization_context()->group_controller =
@@ skipping 19 matching lines @@
 
   uint32_t version_;
 
   DISALLOW_COPY_AND_ASSIGN(InterfacePtrState);
 };
 
 }  // namespace internal
 }  // namespace mojo
 
 #endif  // MOJO_PUBLIC_CPP_BINDINGS_LIB_INTERFACE_PTR_STATE_H_