Implement basic USB device enumeration on Android.

device/usb/usb_service_android.h

 // 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.
 
 #ifndef DEVICE_USB_USB_SERVICE_ANDROID_H_
 #define DEVICE_USB_USB_SERVICE_ANDROID_H_
 
+#include <string>
+
+#include "base/android/scoped_java_ref.h"
 #include "device/usb/usb_service.h"
 
 namespace device {
 
 // USB service implementation for Android. This is a stub implementation that
 // does not return any devices.
 class UsbServiceAndroid : public UsbService {
  public:
+  // Register C++ methods exposed to Java using JNI.
+  static bool RegisterJNI(JNIEnv* env);
+
   UsbServiceAndroid();
   ~UsbServiceAndroid() override;
 
+  // UsbService:
   scoped_refptr<UsbDevice> GetDevice(const std::string& guid) override;
   void GetDevices(const GetDevicesCallback& callback) override;
+
+ private:
+  // Java object org.chromium.device.usb.ChromeUsbService.
+  base::android::ScopedJavaGlobalRef<jobject> j_object_;
 };
 
 }  // namespace device
 
 #endif  // DEVICE_USB_USB_SERVICE_ANDROID_H_