Introduce IPC::ChannelProxy::Create*() and IPC::SynChannel::Create*()

apps/app_shim/app_shim_host_manager_browsertest_mac.mm

Index: apps/app_shim/app_shim_host_manager_browsertest_mac.mm
diff --git a/apps/app_shim/app_shim_host_manager_browsertest_mac.mm b/apps/app_shim/app_shim_host_manager_browsertest_mac.mm
index c97f544d97416344f1f4169dc4ef8f97a00b6c53..4327e9797ca8a990701103da76a583511d014c41 100644
--- a/apps/app_shim/app_shim_host_manager_browsertest_mac.mm
+++ b/apps/app_shim/app_shim_host_manager_browsertest_mac.mm
@@ -63,8 +63,8 @@ TestShimClient::TestShimClient() : io_thread_("TestShimClientIO") {
   app_mode::VerifySocketPermissions(socket_path);
 
   IPC::ChannelHandle handle(socket_path.value());
-  channel_.reset(new IPC::ChannelProxy(handle, IPC::Channel::MODE_NAMED_CLIENT,
-      this, io_thread_.message_loop_proxy().get()));
+  channel_ = IPC::ChannelProxy::CreateNamedClient(
+      handle, this, io_thread_.message_loop_proxy().get());
 }
 
 TestShimClient::~TestShimClient() {}