[Passwords] Handle null driver in generation popup gracefully

This change gracefully handles a null PasswordManagerDriver in
PasswordGenerationPopupControllerImpl::PasswordAccepted instead of
forcing a CHECK failure.

Bug: 1133635
Change-Id: Ife83a3c8c78b5dff18c3252c3beb0092750d4420
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2463834
Commit-Queue: Jan Wilken Dörrie <jdoerrie@chromium.org>
Reviewed-by: Vasilii Sukhanov <vasilii@chromium.org>
Cr-Commit-Position: refs/heads/master@{#816536}

chrome/browser/ui/passwords/password_generation_popup_controller_impl.cc

@@ -194,9 +194,12 @@ void PasswordGenerationPopupControllerImpl::PasswordAccepted() {
     return;
 
   base::WeakPtr<PasswordGenerationPopupControllerImpl> weak_this = GetWeakPtr();
-  CHECK(driver_);
-  driver_->GeneratedPasswordAccepted(form_data_, generation_element_id_,
-                                     current_password_);
+  if (driver_) {
+    // See https://crbug.com/1133635 for when `driver_` might be null due to a
+    // compromised renderer.
+    driver_->GeneratedPasswordAccepted(form_data_, generation_element_id_,
+                                       current_password_);
+  }
   // |this| can be destroyed here because GeneratedPasswordAccepted pops up
   // another UI and generates some event to close the dropdown.
   if (weak_this)