Bug 1825745 - Make form submits do a replace load if they happen before document load has ended. r=smaug

Differential Revision: https://phabricator.services.mozilla.com/D174224

docshell/base/nsDocShell.h

@@ -710,6 +710,13 @@ class nsDocShell final : public nsDocLoader,
   nsresult ScrollToAnchor(bool aCurHasRef, bool aNewHasRef,
                           nsACString& aNewHash, uint32_t aLoadType);
 
+  // This returns the load type for a form submission (see
+  // https://html.spec.whatwg.org/#form-submission-algorithm). The load type
+  // should be set as soon as the target BC has been determined.
+  uint32_t GetLoadTypeForFormSubmission(
+      mozilla::dom::BrowsingContext* aTargetBC,
+      nsDocShellLoadState* aLoadState);
+
  private:
   // Returns true if would have called FireOnLocationChange,
   // but did not because aFireOnLocationChange was false on entry.