--- a/docshell/base/LoadContext.cpp
+++ b/docshell/base/LoadContext.cpp
@@ -6,29 +6,38 @@
 
 #include "mozilla/Assertions.h"
 #include "mozilla/LoadContext.h"
 
 namespace mozilla {
 
 NS_IMPL_ISUPPORTS(LoadContext, nsILoadContext, nsIInterfaceRequestor)
 
-LoadContext::LoadContext(nsIPrincipal* aPrincipal)
+LoadContext::LoadContext(nsIPrincipal* aPrincipal, nsILoadContext* aOptionalBase)
   : mTopFrameElement(nullptr)
   , mNestedFrameId(0)
   , mIsContent(true)
   , mUsePrivateBrowsing(false)
   , mUseRemoteTabs(false)
 #ifdef DEBUG
   , mIsNotNull(true)
 #endif
 {
   MOZ_ALWAYS_TRUE(NS_SUCCEEDED(aPrincipal->GetAppId(&mAppId)));
   MOZ_ALWAYS_TRUE(NS_SUCCEEDED(
     aPrincipal->GetIsInBrowserElement(&mIsInBrowserElement)));
+
+  if (!aOptionalBase) {
+    return;
+  }
+
+  MOZ_ALWAYS_TRUE(NS_SUCCEEDED(aOptionalBase->GetIsContent(&mIsContent)));
+  MOZ_ALWAYS_TRUE(NS_SUCCEEDED(
+    aOptionalBase->GetUsePrivateBrowsing(&mUsePrivateBrowsing)));
+  MOZ_ALWAYS_TRUE(NS_SUCCEEDED(aOptionalBase->GetUseRemoteTabs(&mUseRemoteTabs)));
 }
 
 //-----------------------------------------------------------------------------
 // LoadContext::nsILoadContext
 //-----------------------------------------------------------------------------
 
 NS_IMETHODIMP
 LoadContext::GetAssociatedWindow(nsIDOMWindow**)

--- a/docshell/base/LoadContext.h
+++ b/docshell/base/LoadContext.h
@@ -102,17 +102,18 @@ public:
     , mIsInBrowserElement(false)
 #ifdef DEBUG
     , mIsNotNull(true)
 #endif
   {}
 
   // Constructor for creating a LoadContext with a given principal's appId and
   // browser flag.
-  explicit LoadContext(nsIPrincipal* aPrincipal);
+  explicit LoadContext(nsIPrincipal* aPrincipal,
+                       nsILoadContext* aOptionalBase = nullptr);
 
 private:
   ~LoadContext() {}
 
   nsWeakPtr     mTopFrameElement;
   uint64_t      mNestedFrameId;
   uint32_t      mAppId;
   bool          mIsContent;