From 416ce4eb694b386f5dc3e067e7008d92e1b024ee Mon Sep 17 00:00:00 2001
From: wolfbeast <mcwerewolf@gmail.com>
Date: Thu, 1 Nov 2018 20:16:11 +0100
Subject: [PATCH] Protect main thread in-process access to WinCompositorWidget
 transparent surface.

---
 .../windows/InProcessWinCompositorWidget.cpp  | 25 +++++++++++++++++++
 widget/windows/InProcessWinCompositorWidget.h |  4 +++
 2 files changed, 29 insertions(+)

diff --git a/widget/windows/InProcessWinCompositorWidget.cpp b/widget/windows/InProcessWinCompositorWidget.cpp
index 685eaf5ca6..a11790b328 100644
--- a/widget/windows/InProcessWinCompositorWidget.cpp
+++ b/widget/windows/InProcessWinCompositorWidget.cpp
@@ -23,6 +23,31 @@ InProcessWinCompositorWidget::InProcessWinCompositorWidget(const CompositorWidge
   MOZ_ASSERT(mWindow);
 }
 
+void
+InProcessWinCompositorWidget::OnDestroyWindow()
+{
+  EnterPresentLock();
+  WinCompositorWidget::OnDestroyWindow();
+  LeavePresentLock();
+}
+
+void
+InProcessWinCompositorWidget::UpdateTransparency(nsTransparencyMode aMode)
+{
+  EnterPresentLock();
+  WinCompositorWidget::UpdateTransparency(aMode);
+  LeavePresentLock();
+}
+
+void
+InProcessWinCompositorWidget::ClearTransparentWindow()
+{
+  EnterPresentLock();
+  WinCompositorWidget::ClearTransparentWindow();
+  LeavePresentLock();
+}
+
+
 nsIWidget*
 InProcessWinCompositorWidget::RealWidget()
 {
diff --git a/widget/windows/InProcessWinCompositorWidget.h b/widget/windows/InProcessWinCompositorWidget.h
index 2ce6ba0be1..afe5a7f535 100644
--- a/widget/windows/InProcessWinCompositorWidget.h
+++ b/widget/windows/InProcessWinCompositorWidget.h
@@ -22,6 +22,10 @@ class InProcessWinCompositorWidget final : public WinCompositorWidget
 public:
   InProcessWinCompositorWidget(const CompositorWidgetInitData& aInitData, nsWindow* aWindow);
 
+  void OnDestroyWindow() override;
+  void UpdateTransparency(nsTransparencyMode aMode) override;
+  void ClearTransparentWindow() override;
+
   void ObserveVsync(VsyncObserver* aObserver) override;
   nsIWidget* RealWidget() override;