Add DesktopCapturer GetSourceList SelectSource FocusOnSelectedSource functions

webrtc/modules/desktop_capture/screen_capturer.cc

+/*
+ *  Copyright (c) 2016 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/screen_capturer.h"
+
+#include <memory>
+#include <utility>
+
+namespace webrtc {
+
+ScreenCapturer::~ScreenCapturer() = default;
+
+bool ScreenCapturer::GetScreenList(ScreenList* screens) {
+  SourceList sources;
+  if (!GetSourceList(&sources)) {
+    return false;
+  }
+
+  for (const Source& source : sources) {
+    if (source.type == SourceType::SCREEN) {
+      screens->push_back({source.screen_id()});
+    }
+  }
+  return true;
+}
+
+bool ScreenCapturer::SelectScreen(ScreenId id) {
+  return SelectSource(Source::NewScreen(id));
+}
+
+bool ScreenCapturer::GetSourceList(SourceList* sources) {
+  ScreenList screens;
+  if (!GetScreenList(&screens)) {
+    return false;
+  }
+
+  for (const Screen& screen : screens) {
+    sources->push_back(Source::NewScreen(screen.id));
+  }
+
+  return true;
+}
+
+bool ScreenCapturer::SelectSource(const Source& source) {
+  if (source.type != SourceType::SCREEN) {
+    return false;
+  }
+
+  return SelectScreen(source.screen_id());
+}
+
+}  // namespace webrtc