Fix assistant autotest api to handle more ready states

It is possible that more than one states indicate ready state,
e.g. |VISIBLE|.

Bug: None
Test: locally run multiple tast tests in sequence
Change-Id: I2ad3a89e7bc0839c60a78f6b3c4360ff05b27a35
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1836022
Commit-Queue: Xiaohui Chen <xiaohuic@chromium.org>
Reviewed-by: Achuith Bhandarkar <achuith@chromium.org>
Cr-Commit-Position: refs/heads/master@{#702464}

chrome/browser/chromeos/extensions/autotest_private/autotest_private_api.cc

@@ -1717,9 +1717,11 @@ AutotestPrivateSetAssistantEnabledFunction::Run() {
   if (!err_msg.empty())
     return RespondNow(Error(err_msg));
 
-  auto new_state = params->enabled ? ash::mojom::AssistantState::READY
-                                   : ash::mojom::AssistantState::NOT_READY;
-  if (ash::AssistantState::Get()->assistant_state() == new_state)
+  // Any state that's not |NOT_READY| would be considered a ready state.
+  const bool not_ready = (ash::AssistantState::Get()->assistant_state() ==
+                          ash::mojom::AssistantState::NOT_READY);
+  const bool success = (params->enabled != not_ready);
+  if (success)
     return RespondNow(NoArguments());
 
   // Assistant service has not responded yet, set up a delayed timer to wait for