[CEX] Fix native action promise crash

(cherry picked from commit aa24f63)

Bug: 1326397
Change-Id: Idd3c72e3a5e4f6e40fdbf134fcc313a7166c0ee4
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3650721
Reviewed-by: Clemens Arbesser <arbesser@google.com>
Auto-Submit: Florian Gauger <fga@google.com>
Commit-Queue: Florian Gauger <fga@google.com>
Cr-Original-Commit-Position: refs/heads/main@{#1004288}
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3662940
Bot-Commit: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com>
Commit-Queue: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com>
Cr-Commit-Position: refs/branch-heads/5060@{#213}
Cr-Branched-From: b83393d-refs/heads/main@{#1002911}

components/autofill_assistant/browser/actions/js_flow_action.cc

@@ -109,6 +109,11 @@ void JsFlowAction::InternalProcessAction(ProcessActionCallback callback) {
 void JsFlowAction::OnFlowFinished(ProcessActionCallback callback,
                                   const ClientStatus& status,
                                   std::unique_ptr<base::Value> return_value) {
+  // Since we can not know in advance how many native actions need to be run
+  // we will create a dangling promise. By destroying the flow executor we make
+  // sure that these will not be executed.
+  js_flow_executor_.reset(nullptr);
+
   UpdateProcessedAction(status);
 
   // If the flow returned a value, we extract the status and possibly a flow

components/autofill_assistant/browser/js_flow_executor_impl.cc

@@ -388,6 +388,7 @@ void JsFlowExecutorImpl::RunCallback(
     VLOG(1) << "Flow failed with " << status
             << " and result: " << *result_value;
   }
+
   std::move(callback_).Run(status, std::move(result_value));
 }