Remove differ from ScreenCapturer implementations

webrtc/modules/desktop_capture/win/screen_capturer_win_magnifier.h

Index: webrtc/modules/desktop_capture/win/screen_capturer_win_magnifier.h
diff --git a/webrtc/modules/desktop_capture/win/screen_capturer_win_magnifier.h b/webrtc/modules/desktop_capture/win/screen_capturer_win_magnifier.h
index 969cb83bcfaa31e859e26cf60905d733e7e8c036..99d8d1b9eb22a430722585d87f71a9240bf7c8dc 100644
--- a/webrtc/modules/desktop_capture/win/screen_capturer_win_magnifier.h
+++ b/webrtc/modules/desktop_capture/win/screen_capturer_win_magnifier.h
@@ -29,7 +29,6 @@ namespace webrtc {
 
 class DesktopFrame;
 class DesktopRect;
-class Differ;
 
 // Captures the screen using the Magnification API to support window exclusion.
 // Each capturer must run on a dedicated thread because it uses thread local
@@ -116,9 +115,6 @@ class ScreenCapturerWinMagnifier : public ScreenCapturer {
   // Queue of the frames buffers.
   ScreenCaptureFrameQueue<SharedDesktopFrame> queue_;
 
-  // Class to calculate the difference between two screen bitmaps.
-  std::unique_ptr<Differ> differ_;
-
   ScopedThreadDesktop desktop_;
 
   // Used for getting the screen dpi.