Ignore updates to app list Most Likely apps when animating off the start page.

This CL ignores updates to and disables the Most Likely apps when the page is
animating away from the start page. This prevents the apps from disappearing
due to a search being initiated.

BUG=454667

Review URL: https://codereview.chromium.org/897583002

Cr-Commit-Position: refs/heads/master@{#314746}

ui/app_list/views/app_list_view_unittest.cc

@@ -478,6 +478,7 @@ void AppListViewTestContext::RunStartPageTest() {
     EXPECT_EQ(view_size.ToString(), view_->GetPreferredSize().ToString());
 
     // Check tiles hide and show on deletion and addition.
+    EXPECT_TRUE(SetAppListState(AppListModel::STATE_START));
     model->results()->Add(new TestStartPageSearchResult());
     start_page_view->UpdateForTesting();
     EXPECT_EQ(1u, GetVisibleViews(start_page_view->tile_views()));

ui/app_list/views/start_page_view.cc

@@ -68,7 +68,8 @@ class SearchBoxSpacerView : public views::View {
 class StartPageView::StartPageTilesContainer
     : public SearchResultContainerView {
  public:
-  explicit StartPageTilesContainer(AllAppsTileItemView* all_apps_button);
+  StartPageTilesContainer(ContentsView* contents_view,
+                          AllAppsTileItemView* all_apps_button);
   ~StartPageTilesContainer() override;
 
   TileItemView* GetTileItemView(size_t index);
@@ -85,6 +86,8 @@ class StartPageView::StartPageTilesContainer
   void OnContainerSelected(bool from_bottom) override;
 
  private:
+  ContentsView* contents_view_;
+
   std::vector<SearchResultTileItemView*> search_result_tile_views_;
   AllAppsTileItemView* all_apps_button_;
 
@@ -92,8 +95,9 @@ class StartPageView::StartPageTilesContainer
 };
 
 StartPageView::StartPageTilesContainer::StartPageTilesContainer(
+    ContentsView* contents_view,
     AllAppsTileItemView* all_apps_button)
-    : all_apps_button_(all_apps_button) {
+    : contents_view_(contents_view), all_apps_button_(all_apps_button) {
   views::BoxLayout* tiles_layout_manager =
       new views::BoxLayout(views::BoxLayout::kHorizontal, 0, 0, kTileSpacing);
   tiles_layout_manager->set_main_axis_alignment(
@@ -129,16 +133,26 @@ TileItemView* StartPageView::StartPageTilesContainer::GetTileItemView(
 }
 
 int StartPageView::StartPageTilesContainer::Update() {
+  // Ignore updates and disable buttons when transitioning to a different
+  // state.
+  if (contents_view_->GetActiveState() != AppListModel::STATE_START) {
+    for (auto* view : search_result_tile_views_)
+      view->SetEnabled(false);
+
+    return num_results();
+  }
+
   std::vector<SearchResult*> display_results =
       AppListModel::FilterSearchResultsByDisplayType(
           results(), SearchResult::DISPLAY_RECOMMENDATION, kNumStartPageTiles);
 
   // Update the tile item results.
   for (size_t i = 0; i < search_result_tile_views_.size(); ++i) {
-    SearchResult* item = nullptr;
+    SearchResult* item = NULL;
     if (i < display_results.size())
       item = display_results[i];
     search_result_tile_views_[i]->SetSearchResult(item);
+    search_result_tile_views_[i]->SetEnabled(true);
   }
 
   Layout();
@@ -170,9 +184,11 @@ StartPageView::StartPageView(AppListMainView* app_list_main_view,
       search_box_spacer_view_(new SearchBoxSpacerView(
           app_list_main_view->search_box_view()->GetPreferredSize())),
       instant_container_(new views::View),
-      tiles_container_(new StartPageTilesContainer(new AllAppsTileItemView(
-          app_list_main_view_->contents_view(),
-          view_delegate_->GetModel()->top_level_item_list()))) {
+      tiles_container_(new StartPageTilesContainer(
+          app_list_main_view->contents_view(),
+          new AllAppsTileItemView(
+              app_list_main_view_->contents_view(),
+              view_delegate_->GetModel()->top_level_item_list()))) {
   // The view containing the start page WebContents and SearchBoxSpacerView.
   InitInstantContainer();
   AddChildView(instant_container_);