ipc: Remove unnecessary attachment broker plumbing.

content/test/render_thread_impl_browser_test_ipc_helper.cc

Index: content/test/render_thread_impl_browser_test_ipc_helper.cc
diff --git a/content/test/render_thread_impl_browser_test_ipc_helper.cc b/content/test/render_thread_impl_browser_test_ipc_helper.cc
index 7a4bec189540e42f088e76493808c18bde15ebfe..8f454e2a7b72ba8f9322cbb935f4f5450afe94ae 100644
--- a/content/test/render_thread_impl_browser_test_ipc_helper.cc
+++ b/content/test/render_thread_impl_browser_test_ipc_helper.cc
@@ -28,7 +28,7 @@ RenderThreadImplBrowserIPCTestHelper::RenderThreadImplBrowserIPCTestHelper() {
   } else {
     channel_ = IPC::ChannelProxy::Create(channel_id_, IPC::Channel::MODE_SERVER,
                                          dummy_listener_.get(),
-                                         ipc_thread_->task_runner(), nullptr);
+                                         ipc_thread_->task_runner());
   }
 }
 
@@ -52,7 +52,7 @@ void RenderThreadImplBrowserIPCTestHelper::SetupMojo() {
 
   channel_ = IPC::ChannelProxy::Create(
       IPC::ChannelMojo::CreateServerFactory(ipc_thread_->task_runner(),
-                                            channel_id_, nullptr),
+                                            channel_id_),
       dummy_listener_.get(), ipc_thread_->task_runner());
 
   mojo_application_host_->Init();