Mojo C++ bindings: remove some usage of AssociatedGroup from user code.

mojo/public/cpp/bindings/tests/bind_task_runner_unittest.cc

 // Copyright 2016 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.
 
 #include "base/bind.h"
 #include "base/callback.h"
 #include "base/message_loop/message_loop.h"
 #include "base/single_thread_task_runner.h"
 #include "base/synchronization/lock.h"
 #include "base/synchronization/waitable_event.h"
 #include "base/threading/platform_thread.h"
 #include "mojo/public/cpp/bindings/associated_binding.h"
-#include "mojo/public/cpp/bindings/associated_group.h"
 #include "mojo/public/cpp/bindings/associated_interface_ptr.h"
 #include "mojo/public/cpp/bindings/associated_interface_ptr_info.h"
 #include "mojo/public/cpp/bindings/associated_interface_request.h"
 #include "mojo/public/cpp/bindings/binding.h"
 #include "mojo/public/interfaces/bindings/tests/test_associated_interfaces.mojom.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
 namespace mojo {
 namespace test {
 namespace {
@@ skipping 191 matching lines @@
     auto connection_request =
         MakeRequest(&connection_ptr_, connection_ptr_task_runner_);
     connection_impl_.reset(new IntegerSenderConnectionImpl(
         std::move(connection_request), connection_binding_task_runner_,
         sender_binding_task_runner_));
 
     connection_impl_->set_get_sender_notification(
         base::Bind(&AssociatedBindTaskRunnerTest::QuitTaskRunner,
                    base::Unretained(this)));
 
-    connection_ptr_->GetSender(MakeRequest(&sender_ptr_,
-                                           connection_ptr_.associated_group(),
-                                           sender_ptr_task_runner_));
+    connection_ptr_->GetSender(
+        MakeRequest(&sender_ptr_, nullptr, sender_ptr_task_runner_));
     connection_binding_task_runner_->Run();
   }
 
   void QuitTaskRunner() {
     connection_binding_task_runner_->Quit();
   }
 
   base::MessageLoop loop_;
   scoped_refptr<TestTaskRunner> connection_binding_task_runner_;
   scoped_refptr<TestTaskRunner> connection_ptr_task_runner_;
@@ skipping 148 matching lines @@
   EXPECT_TRUE(sender_impl_error);
   connection_ptr_task_runner_->Run();
   EXPECT_TRUE(connection_ptr_error);
   sender_ptr_task_runner_->Run();
   EXPECT_TRUE(sender_ptr_error);
 }
 
 }  // namespace
 }  // namespace test
 }  // namespace mojo