Implement basic USB device enumeration on Android.

device/usb/usb_service_android.h

Index: device/usb/usb_service_android.h
diff --git a/device/usb/usb_service_android.h b/device/usb/usb_service_android.h
index d1ffd9dffaea52a8b6bf5f5faa196072022f289c..9cab43851716cbccbd4b31b58cf8896492ad0d89 100644
--- a/device/usb/usb_service_android.h
+++ b/device/usb/usb_service_android.h
@@ -5,6 +5,9 @@
 #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 {
@@ -13,11 +16,19 @@ namespace device {
 // 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