Support USB device hotplug 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 <unordered_map>
 
 #include "base/android/scoped_java_ref.h"
 #include "device/usb/usb_service.h"
 
 namespace device {
 
+class UsbDeviceAndroid;
+
 // 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;
 
+  // Methods called by Java.
+  void DeviceAttached(JNIEnv* env,
+                      const base::android::JavaRef<jobject>& caller,
+                      const base::android::JavaRef<jobject>& usb_device);
+  void DeviceDetached(JNIEnv* env,
+                      const base::android::JavaRef<jobject>& caller,
+                      jint device_id);
+
  private:
+  void AddDevice(scoped_refptr<UsbDeviceAndroid> device);
+
+  std::unordered_map<jint, scoped_refptr<UsbDeviceAndroid>> devices_by_id_;
+  std::unordered_map<std::string, scoped_refptr<UsbDeviceAndroid>>
+      devices_by_guid_;
+
   // Java object org.chromium.device.usb.ChromeUsbService.
   base::android::ScopedJavaGlobalRef<jobject> j_object_;
 };
 
 }  // namespace device
 
 #endif  // DEVICE_USB_USB_SERVICE_ANDROID_H_