[DesktopCapture] Detect screen resolution changes in DirectX capturer

webrtc/modules/desktop_capture/resolution_change_detector.h

Index: webrtc/modules/desktop_capture/resolution_change_detector.h
diff --git a/webrtc/modules/desktop_capture/resolution_change_detector.h b/webrtc/modules/desktop_capture/resolution_change_detector.h
new file mode 100644
index 0000000000000000000000000000000000000000..6ccf8a7a171fabda23f5a7602216811a95d2fa85
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+++ b/webrtc/modules/desktop_capture/resolution_change_detector.h
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+/*
+ *  Copyright (c) 2017 The WebRTC project authors. All Rights Reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#ifndef WEBRTC_MODULES_DESKTOP_CAPTURE_RESOLUTION_CHANGE_DETECTOR_H_
+#define WEBRTC_MODULES_DESKTOP_CAPTURE_RESOLUTION_CHANGE_DETECTOR_H_
+
+#include "webrtc/modules/desktop_capture/desktop_geometry.h"
+
+namespace webrtc {
+
+class ResolutionChangeDetector {
+ public:
+  bool IsChanged(DesktopSize size);
+  void Reset();
+
+ private:
+  DesktopSize last_size_;
+  bool initialized_ = false;
+};
+
+}  // namespace webrtc
+
+#endif  // WEBRTC_MODULES_DESKTOP_CAPTURE_RESOLUTION_CHANGE_DETECTOR_H_