Crash in DirectX capturer

webrtc/modules/desktop_capture/win/dxgi_output_duplicator.cc

Index: webrtc/modules/desktop_capture/win/dxgi_output_duplicator.cc
diff --git a/webrtc/modules/desktop_capture/win/dxgi_output_duplicator.cc b/webrtc/modules/desktop_capture/win/dxgi_output_duplicator.cc
index b17c195340b0e495fa6e123a2b33c06141e9a2c5..122ad1f6e159cab692eb28394588145173f075f2 100644
--- a/webrtc/modules/desktop_capture/win/dxgi_output_duplicator.cc
+++ b/webrtc/modules/desktop_capture/win/dxgi_output_duplicator.cc
@@ -16,6 +16,8 @@
 #include <DXGIFormat.h>
 #include <Windows.h>
 
+#include <algorithm>
+
 #include "webrtc/base/checks.h"
 #include "webrtc/base/logging.h"
 #include "webrtc/modules/desktop_capture/win/dxgi_texture_mapping.h"
@@ -274,29 +276,20 @@ void DxgiOutputDuplicator::Setup(Context* context) {
   RTC_DCHECK(context->updated_region.is_empty());
   // Always copy entire monitor during the first Duplicate() function call.
   context->updated_region.AddRect(desktop_rect_);
-  for (size_t i = 0; i < contexts_.size(); i++) {
-    if (contexts_[i] == nullptr) {
-      contexts_[i] = context;
-      return;
-    }
-  }
-
+  RTC_DCHECK(std::find(contexts_.begin(), contexts_.end(), context) ==
+             contexts_.end());
   contexts_.push_back(context);
 }
 
 void DxgiOutputDuplicator::Unregister(const Context* const context) {
-  for (size_t i = 0; i < contexts_.size(); i++) {
-    if (contexts_[i] == context) {
-      contexts_[i] = nullptr;
-      return;
-    }
-  }
-
-  RTC_NOTREACHED();
+  auto it = std::find(contexts_.begin(), contexts_.end(), context);
+  RTC_DCHECK(it != contexts_.end());
+  contexts_.erase(it);
 }
 
 void DxgiOutputDuplicator::SpreadContextChange(const Context* const source) {
   for (Context* dest : contexts_) {
+    RTC_DCHECK(dest);
     if (dest != source) {
       dest->updated_region.AddRegion(source->updated_region);
     }