Bug 1888756, part 2 - Text Fragments: Implement setting the textDirectiveUserActivation flag in the document loading algorithm. r=edgar,dom-core

This commit is a prerequisite for part 5 of this patch set.

This flag is set in the docshell, based on `user gesture activation`.
This is not necessarily sufficient,
as the text fragments spec bases the value of
this flag also on User Involvement, which is not
implemented in Gecko yet.

The flag is then plumbed through the parent process
(`DocumentLoadListener::CreateDocumentLoadInfo()`)
to the document, where it can be consumed.
This includes client-side redirects as described in [0].

There is no changed behavior in this commit.

[0] https://wicg.github.io/scroll-to-text-fragment/#restricting-the-text-fragment

Differential Revision: https://phabricator.services.mozilla.com/D212817

dom/html/HTMLFormElement.cpp

@@ -874,6 +874,13 @@ nsresult HTMLFormElement::SubmitSubmission(
     loadState->SetCsp(GetCsp());
     loadState->SetAllowFocusMove(UserActivation::IsHandlingUserInput());
 
+    const bool hasValidUserGestureActivation =
+        doc->HasValidTransientUserGestureActivation();
+    loadState->SetHasValidUserGestureActivation(hasValidUserGestureActivation);
+    loadState->SetTextDirectiveUserActivation(
+        doc->ConsumeTextDirectiveUserActivation() ||
+        hasValidUserGestureActivation);
+
     nsCOMPtr<nsIPrincipal> nodePrincipal = NodePrincipal();
     rv = container->OnLinkClickSync(this, loadState, false, nodePrincipal);
     NS_ENSURE_SUBMIT_SUCCESS(rv);