Refactored gamepad polling to support dynamic sources

device/gamepad/gamepad_platform_data_fetcher_linux.h

 // Copyright (c) 2012 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_GAMEPAD_GAMEPAD_PLATFORM_DATA_FETCHER_LINUX_H_
 #define DEVICE_GAMEPAD_GAMEPAD_PLATFORM_DATA_FETCHER_LINUX_H_
 
 #include <stddef.h>
 
 #include <memory>
 #include <string>
 
 #include "base/compiler_specific.h"
 #include "base/macros.h"
 #include "device/gamepad/gamepad_data_fetcher.h"
 
 extern "C" {
 struct udev_device;
 }
 
 namespace device {
 class UdevLinux;
 }
 
 namespace device {
 
 class GamepadPlatformDataFetcherLinux : public GamepadDataFetcher {
  public:
+  typedef GamepadDataFetcherFactoryImpl<GamepadPlatformDataFetcherLinux,
+                                        GAMEPAD_SOURCE_LINUX_UDEV>
+      Factory;
+
   GamepadPlatformDataFetcherLinux();
   ~GamepadPlatformDataFetcherLinux() override;
 
+  GamepadSource source() override;
+
   // GamepadDataFetcher implementation.
-  void GetGamepadData(blink::WebGamepads* pads,
-                      bool devices_changed_hint) override;
+  void GetGamepadData(bool devices_changed_hint) override;
 
  private:
+  void OnAddedToProvider() override;
+
   void RefreshDevice(udev_device* dev);
   void EnumerateDevices();
   void ReadDeviceData(size_t index);
 
   // File descriptor for the /dev/input/js* devices. -1 if not in use.
   int device_fd_[blink::WebGamepads::itemsLengthCap];
 
   std::unique_ptr<device::UdevLinux> udev_;
 
   DISALLOW_COPY_AND_ASSIGN(GamepadPlatformDataFetcherLinux);
 };
 
 }  // namespace device
 
 #endif  // DEVICE_GAMEPAD_GAMEPAD_PLATFORM_DATA_FETCHER_LINUX_H_