Reland: Introduce the devices Mojo app

device/core/device_client.h

Index: device/core/device_client.h
diff --git a/device/core/device_client.h b/device/core/device_client.h
index 00fa17902ab70f58e4ea26467a45085fc227f2f1..300f4d69826c579bfd090273cfc67b49dc8d0a42 100644
--- a/device/core/device_client.h
+++ b/device/core/device_client.h
@@ -34,11 +34,6 @@ class DeviceClient {
   // Returns the UsbService instance for this embedder.
   virtual UsbService* GetUsbService();
 
-  // Connects a USB DeviceManager client to a concrete implementation. If
-  // no such implementation is available the request is dropped.
-  virtual void ConnectToUSBDeviceManager(
-      mojo::InterfaceRequest<usb::DeviceManager> request);
-
   // Returns the HidService instance for this embedder.
   virtual HidService* GetHidService();