Reland: Introduce the devices Mojo app

device/usb/public/cpp/BUILD.gn

Index: device/usb/public/cpp/BUILD.gn
diff --git a/device/usb/public/cpp/BUILD.gn b/device/usb/public/cpp/BUILD.gn
deleted file mode 100644
index 43cea68e3dbdea9cc24eb578cc504673656f9242..0000000000000000000000000000000000000000
--- a/device/usb/public/cpp/BUILD.gn
+++ /dev/null
@@ -1,16 +0,0 @@
-# Copyright 2015 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.
-
-source_set("cpp") {
-  sources = [
-    "device_manager_delegate.h",
-    "device_manager_factory.h",
-  ]
-
-  public_deps = [
-    "//base",
-    "//device/usb/public/interfaces",
-    "//third_party/mojo/src/mojo/public/cpp/bindings",
-  ]
-}