Create OmniboxResultViews lazily.

This reduces memory and CPU use during browser startup and more than eliminates
the perf regression from r706189.

Bug: 1021323
Change-Id: I10b4cf053d73fc0b38c89a35f7786635b06986ed
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1900403
Commit-Queue: Peter Kasting <pkasting@chromium.org>
Reviewed-by: Kevin Bailey <krb@chromium.org>
Auto-Submit: Peter Kasting <pkasting@chromium.org>
Cr-Commit-Position: refs/heads/master@{#713476}

chrome/browser/ui/views/omnibox/omnibox_popup_contents_view.cc

@@ -146,13 +146,6 @@ OmniboxPopupContentsView::OmniboxPopupContentsView(
 
   SetLayoutManager(std::make_unique<views::BoxLayout>(
       views::BoxLayout::Orientation::kVertical));
-
-  // TODO(krb): Remove this when we're sure that nothing accesses the
-  // matches between here and UpdatePopupAppearance().
-  for (size_t i = 0; i < AutocompleteResult::GetMaxMatches(); ++i) {
-    AddChildView(std::make_unique<OmniboxResultView>(this, i, theme_provider_))
-        ->SetVisible(false);
-  }
 }
 
 OmniboxPopupContentsView::~OmniboxPopupContentsView() {
@@ -248,14 +241,14 @@ void OmniboxPopupContentsView::UpdatePopupAppearance() {
   // we have enough row views.
   const size_t result_size = model_->result().size();
   for (size_t i = 0; i < result_size; ++i) {
-    // The model can send us more results than we expected when the user
-    // enables loose-limit-on-submatches and has dedicated rows. Add rows to
-    // handle what they've sent.
+    // Create child views lazily.  Since especially the first result view may be
+    // expensive to create due to loading font data, this saves time and memory
+    // during browser startup.
     if (children().size() <= i) {
       AddChildView(
-          std::make_unique<OmniboxResultView>(this, i, theme_provider_))
-          ->SetVisible(false);
+          std::make_unique<OmniboxResultView>(this, i, theme_provider_));
     }
+
     OmniboxResultView* view = result_view_at(i);
     const AutocompleteMatch& match = GetMatchAtIndex(i);
     view->SetMatch(match);

chrome/browser/ui/views/omnibox/omnibox_popup_contents_view_browsertest.cc

@@ -93,6 +93,8 @@ class TestAXEventObserver : public views::AXEventObserver {
 
   // views::AXEventObserver:
   void OnViewEvent(views::View* view, ax::mojom::Event event_type) override {
+    if (!view->GetWidget())
+      return;
     ui::AXNodeData node_data;
     view->GetAccessibleNodeData(&node_data);
     if (event_type == ax::mojom::Event::kTextChanged &&
@@ -330,6 +332,12 @@ IN_PROC_BROWSER_TEST_F(OmniboxPopupContentsViewTest, MAYBE_ClickOmnibox) {
 // color.
 IN_PROC_BROWSER_TEST_F(OmniboxPopupContentsViewTest,
                        PopupMatchesLocationBarBackground) {
+  // In dark mode the omnibox focused and unfocused colors are the same, which
+  // makes this test fail; see comments below.
+  BrowserView::GetBrowserViewForBrowser(browser())
+      ->GetNativeTheme()
+      ->set_use_dark_colors(false);
+
   // Start with the Omnibox unfocused.
   omnibox_view()->GetFocusManager()->ClearFocus();
   const SkColor color_before_focus = location_bar()->background()->get_color();
@@ -420,6 +428,8 @@ IN_PROC_BROWSER_TEST_F(OmniboxPopupContentsViewTest,
   ACMatches matches;
   matches.push_back(match);
   results.AppendMatches(input, matches);
+  results.SortAndCull(input, nullptr);
+  autocomplete_controller->NotifyChanged(true);
 
   // Lets check that arrowing up and down emits the event.
   TestAXEventObserver observer;