Add reference counter of DxgiDuplicatorController to unload DXGI components

webrtc/modules/desktop_capture/win/dxgi_duplicator_controller.cc

Index: webrtc/modules/desktop_capture/win/dxgi_duplicator_controller.cc
diff --git a/webrtc/modules/desktop_capture/win/dxgi_duplicator_controller.cc b/webrtc/modules/desktop_capture/win/dxgi_duplicator_controller.cc
index c17bd1481c7fffa9e09939e3fbcb75f70deaee87..a0bc95fff10e766cffa0174e75a550a2a0d02660 100644
--- a/webrtc/modules/desktop_capture/win/dxgi_duplicator_controller.cc
+++ b/webrtc/modules/desktop_capture/win/dxgi_duplicator_controller.cc
@@ -16,6 +16,7 @@
 #include <string>
 
 #include "webrtc/base/checks.h"
+#include "webrtc/base/logging.h"
 #include "webrtc/base/timeutils.h"
 #include "webrtc/modules/desktop_capture/desktop_capture_types.h"
 #include "webrtc/modules/desktop_capture/win/dxgi_frame.h"
@@ -25,18 +26,30 @@
 namespace webrtc {
 
 // static
-DxgiDuplicatorController* DxgiDuplicatorController::Instance() {
+rtc::scoped_refptr<DxgiDuplicatorController>
+DxgiDuplicatorController::Instance() {
   // The static instance won't be deleted to ensure it can be used by other
   // threads even during program exiting.
   static DxgiDuplicatorController* instance = new DxgiDuplicatorController();
-  return instance;
+  return rtc::scoped_refptr<DxgiDuplicatorController>(instance);
 }
 
-DxgiDuplicatorController::DxgiDuplicatorController() = default;
+DxgiDuplicatorController::DxgiDuplicatorController()
+    : refcount_(0) {}
 
-DxgiDuplicatorController::~DxgiDuplicatorController() {
-  rtc::CritScope lock(&lock_);
-  Deinitialize();
+void DxgiDuplicatorController::AddRef() {
+  int refcount = (++refcount_);
+  RTC_DCHECK(refcount > 0);
+}
+
+void DxgiDuplicatorController::Release() {
+  int refcount = (--refcount_);
+  RTC_DCHECK(refcount >= 0);
+  if (refcount == 0) {
+    LOG(LS_WARNING) << "Count of references reaches zero, "
+                       "DxgiDuplicatorController will be unloaded.";
+    Unload();
+  }
 }
 
 bool DxgiDuplicatorController::IsSupported() {
@@ -129,6 +142,11 @@ DxgiDuplicatorController::DoDuplicate(DxgiFrame* frame, int monitor_id) {
   return Result::DUPLICATION_FAILED;
 }
 
+void DxgiDuplicatorController::Unload() {
+  rtc::CritScope lock(&lock_);
+  Deinitialize();
+}
+
 void DxgiDuplicatorController::Unregister(const Context* const context) {
   rtc::CritScope lock(&lock_);
   if (ContextExpired(context)) {