Remove MessageLoop destruction observer from //device/usb

device/usb/usb_device_handle_usbfs.h

Index: device/usb/usb_device_handle_usbfs.h
diff --git a/device/usb/usb_device_handle_usbfs.h b/device/usb/usb_device_handle_usbfs.h
index 837bc69ece92c25ae2b493418d141775af22893a..2b9044558cf42e7043432e2618c906024875a4f5 100644
--- a/device/usb/usb_device_handle_usbfs.h
+++ b/device/usb/usb_device_handle_usbfs.h
@@ -104,21 +104,11 @@ class UsbDeviceHandleUsbfs : public UsbDeviceHandle {
   };
 
   virtual void CloseBlocking();
-  void SetConfigurationBlocking(int configuration_value,
-                                const ResultCallback& callback);
   void SetConfigurationComplete(int configuration_value,
                                 bool success,
                                 const ResultCallback& callback);
-  void ReleaseInterfaceBlocking(int interface_number,
-                                const ResultCallback& callback);
   void ReleaseInterfaceComplete(int interface_number,
                                 const ResultCallback& callback);
-  void SetInterfaceBlocking(int interface_number,
-                            int alternate_setting,
-                            const ResultCallback& callback);
-  void ResetDeviceBlocking(const ResultCallback& callback);
-  void ClearHaltBlocking(uint8_t endpoint_address,
-                         const ResultCallback& callback);
   void IsochronousTransferInternal(uint8_t endpoint_address,
                                    scoped_refptr<net::IOBuffer> buffer,
                                    size_t total_length,
@@ -160,10 +150,8 @@ class UsbDeviceHandleUsbfs : public UsbDeviceHandle {
   // included in the map.
   std::map<uint8_t, EndpointInfo> endpoints_;
 
-  // Helper object owned by the blocking task thread. It will be freed if that
-  // thread's message loop is destroyed but can also be freed by this class on
-  // destruction.
-  FileThreadHelper* helper_;
+  // Helper object exists on the blocking task thread and must be freed there.
+  std::unique_ptr<FileThreadHelper> helper_;
 
   std::list<std::unique_ptr<Transfer>> transfers_;
 };