app_list: Not to update footer in voice query

This patch does not update fooder, i.e. the suggestion chips during
voice query.

Bug: 924624
Test: manual
Change-Id: Idaae11a321d0d7571aa4d1d4d467066bfc34c0f1
Reviewed-on: https://chromium-review.googlesource.com/c/1487799Reviewed-by: Xiaohui Chen <xiaohuic@chromium.org>
Reviewed-by: Xiyuan Xia <xiyuan@chromium.org>
Commit-Queue: Tao Wu <wutao@chromium.org>
Cr-Commit-Position: refs/heads/master@{#635618}

ash/app_list/views/assistant/assistant_main_stage.cc

@@ -222,11 +222,6 @@ void AssistantMainStage::OnCommittedQueryChanged(
 void AssistantMainStage::OnPendingQueryChanged(
     const ash::AssistantQuery& query) {
   query_view_->SetQuery(query);
-  UpdateFooter();
-}
-
-void AssistantMainStage::OnPendingQueryCleared() {
-  UpdateFooter();
 }
 
 void AssistantMainStage::OnResponseChanged(

ash/app_list/views/assistant/assistant_main_stage.h

@@ -50,7 +50,6 @@ class APP_LIST_EXPORT AssistantMainStage
   // AssistantInteractionModelObserver:
   void OnCommittedQueryChanged(const ash::AssistantQuery& query) override;
   void OnPendingQueryChanged(const ash::AssistantQuery& query) override;
-  void OnPendingQueryCleared() override;
   void OnResponseChanged(
       const std::shared_ptr<ash::AssistantResponse>& response) override;