electron/patches/common/webrtc/webrtc-desktop_capturer_mac.patch

diff --git a/modules/desktop_capture/mac/screen_capturer_mac.mm b/modules/desktop_capture/mac/screen_capturer_mac.mm
index df18777226..6a1e3da6ab 100644
--- a/modules/desktop_capture/mac/screen_capturer_mac.mm
+++ b/modules/desktop_capture/mac/screen_capturer_mac.mm
@@ -16,6 +16,7 @@
 #include "rtc_base/checks.h"
 #include "rtc_base/constructormagic.h"
 #include "rtc_base/logging.h"
+#include "rtc_base/synchronization/rw_lock_wrapper.h"
 #include "rtc_base/timeutils.h"
 #include "sdk/objc/Framework/Classes/Common/scoped_cftyperef.h"
 
@@ -28,18 +29,31 @@ namespace webrtc {
 // destroy itself once it's done.
 class DisplayStreamManager {
  public:
-  int GetUniqueId() { return ++unique_id_generator_; }
-  void DestroyStream(int unique_id) {
-    auto it = display_stream_wrappers_.find(unique_id);
-    RTC_CHECK(it != display_stream_wrappers_.end());
-    RTC_CHECK(!it->second.active);
-    CFRelease(it->second.stream);
-    display_stream_wrappers_.erase(it);
+  DisplayStreamManager() : rw_lock_(RWLockWrapper::CreateRWLock()) {}
+  RWLockWrapper* GetLock() {return rw_lock_.get();};
 
-    if (ready_for_self_destruction_ && display_stream_wrappers_.empty()) delete this;
+  int GetUniqueId() {
+    WriteLockScoped scoped_display_stream_manager_lock(*rw_lock_);
+    return ++unique_id_generator_;
+  }
+  void DestroyStream(int unique_id) {
+    bool finalize;
+    {
+      WriteLockScoped scoped_display_stream_manager_lock(*rw_lock_);
+      auto it = display_stream_wrappers_.find(unique_id);
+      RTC_CHECK(it != display_stream_wrappers_.end());
+      RTC_CHECK(!it->second.active);
+      CFRelease(it->second.stream);
+      display_stream_wrappers_.erase(it);
+      finalize = ready_for_self_destruction_ && display_stream_wrappers_.empty();
+    }
+    if (finalize) {
+      delete this;
+    }
   }
 
   void SaveStream(int unique_id, CGDisplayStreamRef stream) {
+    WriteLockScoped scoped_display_stream_manager_lock(*rw_lock_);
     RTC_CHECK(unique_id <= unique_id_generator_);
     DisplayStreamWrapper wrapper;
     wrapper.stream = stream;
@@ -47,6 +61,7 @@ class DisplayStreamManager {
   }
 
   void UnregisterActiveStreams() {
+    WriteLockScoped scoped_display_stream_manager_lock(*rw_lock_);
     for (auto& pair : display_stream_wrappers_) {
       DisplayStreamWrapper& wrapper = pair.second;
       if (wrapper.active) {
@@ -61,12 +76,23 @@ class DisplayStreamManager {
   void PrepareForSelfDestruction() {
     ready_for_self_destruction_ = true;
 
-    if (display_stream_wrappers_.empty()) delete this;
+    bool finalize;
+    {
+      WriteLockScoped scoped_display_stream_manager_lock(*rw_lock_);
+      ready_for_self_destruction_ = true;
+      finalize = display_stream_wrappers_.empty();
+    }
+    if (finalize) {
+      delete this;
+    }
   }
 
   // Once the DisplayStreamManager is ready for destruction, the
   // ScreenCapturerMac is no longer present. Any updates should be ignored.
-  bool ShouldIgnoreUpdates() { return ready_for_self_destruction_; }
+  // Note: not thread-safe! Acquire and release a lock manually.
+  bool ShouldIgnoreUpdates() {
+     return ready_for_self_destruction_;
+  }
 
  private:
   struct DisplayStreamWrapper {
@@ -81,6 +107,7 @@ class DisplayStreamManager {
   std::map<int, DisplayStreamWrapper> display_stream_wrappers_;
   int unique_id_generator_ = 0;
   bool ready_for_self_destruction_ = false;
+  std::unique_ptr<RWLockWrapper> rw_lock_;
 };
 
 namespace {
@@ -507,8 +534,6 @@ bool ScreenCapturerMac::RegisterRefreshAndMoveHandlers() {
         return;
       }
 
-      if (manager->ShouldIgnoreUpdates()) return;
-
       // Only pay attention to frame updates.
       if (status != kCGDisplayStreamFrameStatusFrameComplete) return;
 
@@ -518,7 +543,12 @@ bool ScreenCapturerMac::RegisterRefreshAndMoveHandlers() {
       if (count != 0) {
         // According to CGDisplayStream.h, it's safe to call
         // CGDisplayStreamStop() from within the callback.
-        ScreenRefresh(count, rects, display_origin);
+        manager->GetLock()->AcquireLockShared();
+        bool screen_capturer_mac_invalidated = manager->ShouldIgnoreUpdates();
+        if (!screen_capturer_mac_invalidated) {
+          ScreenRefresh(count, rects, display_origin);
+        }
+        manager->GetLock()->ReleaseLockShared();
       }
     };