Bug 1731982 - Part 11: Set the `IsThirdPartyContextToTopWindow` flag to the main worker script loading channel. r=asuth

When loading the main worker script, we will need to get the clientInfo
for the loading channel. However, the loading channel is created in
content processes and the `IsThirdPartyContextToTopWindow` won't be set
in this case. So, we will get an incorrect clientInfo with a wrong
foreign patitioned principal.

To resolve this, we have to set the flag in the content processes so
that we can get a correct clientInfo. The flag comes from the
workerPrivate which reflects the fact if the worker was created in a
third-party context. And the loading channel should have the same flag
as the document which creates the worker.

Differential Revision: https://phabricator.services.mozilla.com/D129060

dom/workers/ScriptLoader.cpp

@@ -51,6 +51,7 @@
 #include "nsXPCOM.h"
 #include "xpcpublic.h"
 
+#include "mozilla/AntiTrackingUtils.h"
 #include "mozilla/ArrayAlgorithm.h"
 #include "mozilla/Assertions.h"
 #include "mozilla/LoadContext.h"
@@ -1103,6 +1104,15 @@ class ScriptLoaderRunnable final : public nsIRunnable, public nsINamed {
 
     if (IsMainWorkerScript()) {
       MOZ_DIAGNOSTIC_ASSERT(aLoadInfo.mReservedClientInfo.isSome());
+
+      // In order to get the correct foreign partitioned prinicpal, we need to
+      // set the `IsThirdPartyContextToTopWindow` to the channel's loadInfo.
+      // This flag reflects the fact that if the worker is created under a
+      // third-party context.
+      nsCOMPtr<nsILoadInfo> loadInfo = channel->LoadInfo();
+      loadInfo->SetIsThirdPartyContextToTopWindow(
+          mWorkerPrivate->IsThirdPartyContextToTopWindow());
+
       rv = AddClientChannelHelper(
           channel, std::move(aLoadInfo.mReservedClientInfo),
           Maybe<ClientInfo>(), mWorkerPrivate->HybridEventTarget());