Bug 1633401 - Make Document.HasStorageAccess fission compatible. r=baku

In Document::HasStorageAccess(), we try to get the top-level document.
To check if the document is first-party to the top-level document. But,
this won't work for Fission since the top-level document could be
out-of-process.

In this patch, we use broswing context to get the top-level principal to
test if the document is thrid-party. If we cannot get the top-level
outer window, the top-level document should be cross-origin. So, we know
the answer. If the top-level document is available, we check the
principal to see if the document is first-party.

Differential Revision: https://phabricator.services.mozilla.com/D72664

dom/base/Document.cpp

@@ -15578,14 +15578,22 @@ already_AddRefed<mozilla::dom::Promise> Document::HasStorageAccess(
     return promise.forget();
   }
 
-  nsCOMPtr<Document> topLevelDoc = GetTopLevelContentDocument();
-  if (!topLevelDoc) {
-    aRv.Throw(NS_ERROR_NOT_AVAILABLE);
-    return nullptr;
-  }
-  if (topLevelDoc->NodePrincipal()->Equals(NodePrincipal())) {
-    promise->MaybeResolve(true);
-    return promise.forget();
+  RefPtr<BrowsingContext> topBC = GetBrowsingContext()->Top();
+  // We check if the document is a first-party document here by testing if the
+  // top-level window is same-origin. In non-Fission mode, we can directly get
+  // the top-level window through the top browsing context since it should be
+  // in-process. And test their principals.
+  //
+  // In Fission mode, we can also directly get the top-level window. If we
+  // cannot get it, this means the top-level window is cross-origin. Then, we
+  // know our answer.
+  if (auto* topOuterWindow = topBC->GetDOMWindow()) {
+    if (nsGlobalWindowOuter::Cast(topOuterWindow)
+            ->GetPrincipal()
+            ->Equals(NodePrincipal())) {
+      promise->MaybeResolve(true);
+      return promise.forget();
+    }
   }
 
   nsPIDOMWindowInner* inner = GetInnerWindow();