Bug 1885598: Assert on a passed remoteTypeOverride to avoid footguns r=nika

Differential Revision: https://phabricator.services.mozilla.com/D204791

docshell/base/nsDocShellLoadState.cpp

@@ -901,6 +901,14 @@ void nsDocShellLoadState::SetFileName(const nsAString& aFileName) {
   mFileName = aFileName;
 }
 
+void nsDocShellLoadState::SetRemoteTypeOverride(
+    const nsCString& aRemoteTypeOverride) {
+  MOZ_DIAGNOSTIC_ASSERT(
+      NS_IsAboutBlank(mURI),
+      "Should only have aRemoteTypeOverride for about:blank URIs");
+  mRemoteTypeOverride = mozilla::Some(aRemoteTypeOverride);
+}
+
 const nsCString& nsDocShellLoadState::GetEffectiveTriggeringRemoteType() const {
   // Consider non-errorpage loads from session history as being triggred by the
   // parent process, as we'll validate them against the history entry.

docshell/base/nsDocShellLoadState.h

@@ -323,9 +323,7 @@ class nsDocShellLoadState final {
     return mRemoteTypeOverride;
   }
 
-  void SetRemoteTypeOverride(const nsCString& aRemoteTypeOverride) {
-    mRemoteTypeOverride = mozilla::Some(aRemoteTypeOverride);
-  }
+  void SetRemoteTypeOverride(const nsCString& aRemoteTypeOverride);
 
   void SetWasSchemelessInput(bool aWasSchemelessInput) {
     mWasSchemelessInput = aWasSchemelessInput;