cros: Avoid visible flash when the AppListView is refocused

We call ClearSearch when the AppListView gains focus in tablet mode.
This is one of many things we do to reset the AppListView when the it
(which is always open) is focused as the last open window is closed.

The issue is that ClearSearch actually refreshes the suggestion chips
(causing the visible flash). This refresh is unnecessary because the
chips are already refreshed after an app is launched.

Bug: 979594
Change-Id: I8baec08c78fc8c5439127427de62fddeddfb414c
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1690723
Commit-Queue: Alex Newcomer <newcomer@chromium.org>
Reviewed-by: Tao Wu <wutao@chromium.org>
Cr-Commit-Position: refs/heads/master@{#676161}

ash/app_list/views/app_list_main_view.cc

@@ -85,9 +85,6 @@ void AppListMainView::AddContentsViews() {
   AddChildView(contents_view_);
 
   search_box_view_->set_contents_view(contents_view_);
-
-  // Clear the old query and start search.
-  search_box_view_->ClearSearch();
 }
 
 void AppListMainView::ShowAppListWhenReady() {

ash/app_list/views/contents_view.cc

@@ -137,6 +137,9 @@ void ContentsView::Init(AppListModel* model) {
   GetAppsContainerView()->UpdateSuggestionChips();
 
   ActivePageChanged();
+
+  // Hide the search results initially.
+  ShowSearchResults(false);
 }
 
 void ContentsView::ResetForShow() {

ui/chromeos/search_box/search_box_view_base.cc

@@ -450,6 +450,10 @@ bool SearchBoxViewBase::IsSearchBoxTrimmedQueryEmpty() const {
 }
 
 void SearchBoxViewBase::ClearSearch() {
+  // Avoid setting |search_box_| text to empty if it is already empty.
+  if (search_box_->text() == base::string16())
+    return;
+
   search_box_->SetText(base::string16());
   UpdateButtonsVisisbility();
   // Updates model and fires query changed manually because SetText() above