[DesktopCapture] Detect screen resolution changes in DirectX capturer

webrtc/modules/desktop_capture/resolution_change_detector.cc

+/*
+ *  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.
+ */
+
+#include "webrtc/modules/desktop_capture/resolution_change_detector.h"
+
+namespace webrtc {
+
+bool ResolutionChangeDetector::IsChanged(DesktopSize size) {
+  if (!initialized_) {
+    initialized_ = true;
+    last_size_ = size;
+    return false;
+  }
+
+  return !last_size_.equals(size);
+}
+
+void ResolutionChangeDetector::Reset() {
+  initialized_ = false;
+}
+
+}  // namespace webrtc