app_list: Flex tile results when all results do not fit in results list

Minimal search results page width can be less than the max total
search results tile items width - this cl makes search result tile item
list view flex tile item views, and margins between items when required
(with minimal in-between margins, all possible items should fit neatly
into the search result tile item list).

BUG=None

Change-Id: I3ba6882b88d2a695f25caf2bfef38eec5e96109b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1851231Reviewed-by: Xiyuan Xia <xiyuan@chromium.org>
Commit-Queue: Toni Baržić <tbarzic@chromium.org>
Cr-Commit-Position: refs/heads/master@{#704688}

ash/app_list/views/search_result_tile_item_list_view.cc

@@ -81,33 +81,33 @@ SearchResultTileItemListView::SearchResultTileItemListView(
           app_list_features::IsAppReinstallZeroStateEnabled()),
       max_search_result_tiles_(
           AppListConfig::instance().max_search_result_tiles()) {
-  SetLayoutManager(std::make_unique<views::BoxLayout>(
+  layout_ = SetLayoutManager(std::make_unique<views::BoxLayout>(
       views::BoxLayout::Orientation::kHorizontal,
       gfx::Insets(kItemListVerticalSpacing, kItemListHorizontalSpacing),
       kBetweenItemSpacing));
   for (size_t i = 0; i < max_search_result_tiles_; ++i) {
     if (is_app_reinstall_recommendation_enabled_ ||
         is_play_store_app_search_enabled_) {
-      views::Separator* separator = new views::Separator;
+      views::Separator* separator =
+          AddChildView(std::make_unique<views::Separator>());
       separator->SetVisible(false);
       separator->SetBorder(views::CreateEmptyBorder(
           kSeparatorTopPadding, kSeparatorLeftRightPadding,
           AppListConfig::instance().search_tile_height() - kSeparatorHeight,
           kSeparatorLeftRightPadding));
       separator->SetColor(kSeparatorColor);
-
       separator_views_.push_back(separator);
-      AddChildView(separator);
+      layout_->SetFlexForView(separator, 0);
     }
 
-    SearchResultTileItemView* tile_item = new SearchResultTileItemView(
-        view_delegate, nullptr /* pagination model */,
-        false /* show_in_apps_page */);
+    SearchResultTileItemView* tile_item =
+        AddChildView(std::make_unique<SearchResultTileItemView>(
+            view_delegate, nullptr /* pagination model */,
+            false /* show_in_apps_page */));
     tile_item->set_index_in_container(i);
     tile_item->SetParentBackgroundColor(
         AppListConfig::instance().card_background_color());
     tile_views_.push_back(tile_item);
-    AddChildView(tile_item);
     AddObservedResultView(tile_item);
   }
 
@@ -390,6 +390,14 @@ const char* SearchResultTileItemListView::GetClassName() const {
   return "SearchResultTileItemListView";
 }
 
+void SearchResultTileItemListView::Layout() {
+  const bool flex = GetContentsBounds().width() < GetPreferredSize().width();
+  layout_->SetDefaultFlex(flex ? 1 : 0);
+  layout_->set_between_child_spacing(flex ? 1 : kBetweenItemSpacing);
+
+  views::View::Layout();
+}
+
 void SearchResultTileItemListView::OnShownChanged() {
   SearchResultContainerView::OnShownChanged();
   for (const auto* tile_view : tile_views_) {

ash/app_list/views/search_result_tile_item_list_view.h

@@ -13,8 +13,9 @@
 #include "base/timer/timer.h"
 
 namespace views {
-class Textfield;
+class BoxLayout;
 class Separator;
+class Textfield;
 }  // namespace views
 
 namespace ash {
@@ -40,6 +41,7 @@ class APP_LIST_EXPORT SearchResultTileItemListView
   // Overridden from views::View:
   bool OnKeyPressed(const ui::KeyEvent& event) override;
   const char* GetClassName() const override;
+  void Layout() override;
 
   const std::vector<SearchResultTileItemView*>& tile_views_for_test() const {
     return tile_views_;
@@ -71,8 +73,9 @@ class APP_LIST_EXPORT SearchResultTileItemListView
   std::vector<views::Separator*> separator_views_;
 
   // Owned by the views hierarchy.
-  SearchResultPageView* const search_result_page_view_;
-  views::Textfield* search_box_;
+  SearchResultPageView* const search_result_page_view_ = nullptr;
+  views::Textfield* search_box_ = nullptr;
+  views::BoxLayout* layout_ = nullptr;
 
   base::string16 recent_playstore_query_;