Add CreateWindowCapturer() and CreateScreenCapturer() in DesktopCapturer

webrtc/modules/desktop_capture/screen_capturer_x11.cc

Index: webrtc/modules/desktop_capture/screen_capturer_x11.cc
diff --git a/webrtc/modules/desktop_capture/screen_capturer_x11.cc b/webrtc/modules/desktop_capture/screen_capturer_x11.cc
index 34653ec362adebe7d2501a7319bba287b7fd17d2..fb8446ea4111c2f31d93e287f58cd8285a5f4d91 100644
--- a/webrtc/modules/desktop_capture/screen_capturer_x11.cc
+++ b/webrtc/modules/desktop_capture/screen_capturer_x11.cc
@@ -424,4 +424,18 @@ ScreenCapturer* ScreenCapturer::Create(const DesktopCaptureOptions& options) {
   return capturer.release();
 }
 
+// static
+std::unique_ptr<DesktopCapturer> DesktopCapturer::CreateRawScreenCapturer(
+    const DesktopCaptureOptions& options) {
+  if (!options.x_display())
+    return nullptr;
+
+  std::unique_ptr<ScreenCapturer> capturer(new ScreenCapturerLinux());
+  if (!static_cast<ScreenCapturerLinux*>(capturer.get())->Init(options)) {
+    return nullptr;
+  }
+
+  return capturer;
+}
+
 }  // namespace webrtc