--- a/widget/windows/RemoteBackbuffer.cpp
+++ b/widget/windows/RemoteBackbuffer.cpp
@@ -144,22 +144,23 @@ class SharedImage {
     bitmapInfo.bmiHeader.biBitCount = 32;
     bitmapInfo.bmiHeader.biCompression = BI_RGB;
     void* dummy = nullptr;
     return ::CreateDIBSection(nullptr /*paletteDC*/, &bitmapInfo,
                               DIB_RGB_COLORS, &dummy, mFileMapping,
                               0 /*offset*/);
   }
 
-  HANDLE CreateRemoteFileMapping(DWORD aTargetProcessId) {
-    MOZ_ASSERT(aTargetProcessId);
+  HANDLE CreateRemoteFileMapping(HANDLE aTargetProcess) {
+    MOZ_ASSERT(aTargetProcess);
 
     HANDLE fileMapping = nullptr;
-    if (!ipc::DuplicateHandle(mFileMapping, aTargetProcessId, &fileMapping,
-                              0 /*desiredAccess*/, DUPLICATE_SAME_ACCESS)) {
+    if (!::DuplicateHandle(GetCurrentProcess(), mFileMapping, aTargetProcess,
+                           &fileMapping, 0 /*desiredAccess*/,
+                           FALSE /*inheritHandle*/, DUPLICATE_SAME_ACCESS)) {
       return nullptr;
     }
     return fileMapping;
   }
 
   already_AddRefed<gfx::DrawTarget> CreateDrawTarget() {
     return gfx::Factory::CreateDrawTargetForData(
         gfx::BackendType::CAIRO, mPixelData, IntSize(mWidth, mHeight),
@@ -309,18 +310,18 @@ class PresentableSharedImage {
       }
     }
 
     MOZ_ALWAYS_TRUE(::ReleaseDC(aWindowHandle, windowDC));
 
     return result;
   }
 
-  HANDLE CreateRemoteFileMapping(DWORD aTargetProcessId) {
-    return mSharedImage.CreateRemoteFileMapping(aTargetProcessId);
+  HANDLE CreateRemoteFileMapping(HANDLE aTargetProcess) {
+    return mSharedImage.CreateRemoteFileMapping(aTargetProcess);
   }
 
   already_AddRefed<gfx::DrawTarget> CreateDrawTarget() {
     return mSharedImage.CreateDrawTarget();
   }
 
   void CopyPixelsFrom(const PresentableSharedImage& other) {
     mSharedImage.CopyPixelsFrom(other.mSharedImage);
@@ -339,17 +340,17 @@ class PresentableSharedImage {
   SharedImage mSharedImage;
   HDC mDeviceContext;
   HBITMAP mDIBSection;
   HGDIOBJ mSavedObject;
 };
 
 Provider::Provider()
     : mWindowHandle(nullptr),
-      mTargetProcessId(0),
+      mTargetProcess(nullptr),
       mFileMapping(nullptr),
       mRequestReadyEvent(nullptr),
       mResponseReadyEvent(nullptr),
       mSharedDataPtr(nullptr),
       mStopServiceThread(false),
       mServiceThread(nullptr),
       mBackbuffer() {}
 
@@ -372,25 +373,34 @@ Provider::~Provider() {
 
   if (mRequestReadyEvent) {
     MOZ_ALWAYS_TRUE(::CloseHandle(mRequestReadyEvent));
   }
 
   if (mFileMapping) {
     MOZ_ALWAYS_TRUE(::CloseHandle(mFileMapping));
   }
+
+  if (mTargetProcess) {
+    MOZ_ALWAYS_TRUE(::CloseHandle(mTargetProcess));
+  }
 }
 
 bool Provider::Initialize(HWND aWindowHandle, DWORD aTargetProcessId,
                           nsTransparencyMode aTransparencyMode) {
   MOZ_ASSERT(aWindowHandle);
   MOZ_ASSERT(aTargetProcessId);
 
   mWindowHandle = aWindowHandle;
-  mTargetProcessId = aTargetProcessId;
+
+  mTargetProcess = ::OpenProcess(PROCESS_DUP_HANDLE, FALSE /*inheritHandle*/,
+                                 aTargetProcessId);
+  if (!mTargetProcess) {
+    return false;
+  }
 
   mFileMapping = ::CreateFileMappingW(
       INVALID_HANDLE_VALUE, nullptr /*secattr*/, PAGE_READWRITE, 0 /*sizeHigh*/,
       static_cast<DWORD>(sizeof(SharedData)), nullptr /*name*/);
   if (!mFileMapping) {
     return false;
   }
 
@@ -527,17 +537,17 @@ void Provider::HandleBorrowRequest(Borro
 
   // Preserve the contents of the old backbuffer (if it exists)
   if (mBackbuffer) {
     newBackbuffer->CopyPixelsFrom(*mBackbuffer);
     mBackbuffer.reset();
   }
 
   HANDLE remoteFileMapping =
-      newBackbuffer->CreateRemoteFileMapping(mTargetProcessId);
+      newBackbuffer->CreateRemoteFileMapping(mTargetProcess);
   if (!remoteFileMapping) {
     return;
   }
 
   aResponseData->result = ResponseResult::BorrowSuccess;
   aResponseData->width = width;
   aResponseData->height = height;
   aResponseData->fileMapping = remoteFileMapping;

--- a/widget/windows/RemoteBackbuffer.h
+++ b/widget/windows/RemoteBackbuffer.h
@@ -45,17 +45,17 @@ class Provider {
   void ThreadMain();
 
   void HandleBorrowRequest(BorrowResponseData* aResponseData,
                            bool aAllowSameBuffer);
   void HandlePresentRequest(const PresentRequestData& aRequestData,
                             PresentResponseData* aResponseData);
 
   HWND mWindowHandle;
-  DWORD mTargetProcessId;
+  HANDLE mTargetProcess;
   HANDLE mFileMapping;
   HANDLE mRequestReadyEvent;
   HANDLE mResponseReadyEvent;
   SharedData* mSharedDataPtr;
   bool mStopServiceThread;
   PRThread* mServiceThread;
   std::unique_ptr<PresentableSharedImage> mBackbuffer;
   mozilla::Atomic<nsTransparencyMode, MemoryOrdering::Relaxed>