app_list: assistant_page to search_result_page

This patch modifies the behavior that Back() from assistant_page should
be to the search_result_page.

Bug: 924624
Test: manual
Change-Id: Iba644fee5426ab8b36f47ad4b2e459b1286bd50d
Reviewed-on: https://chromium-review.googlesource.com/c/1455519Reviewed-by: Xiyuan Xia <xiyuan@chromium.org>
Reviewed-by: Xiaohui Chen <xiaohuic@chromium.org>
Commit-Queue: Tao Wu <wutao@chromium.org>
Cr-Commit-Position: refs/heads/master@{#630070}

ash/app_list/views/assistant/assistant_page_view.cc

@@ -22,6 +22,10 @@ namespace {
 constexpr int kHeight = 440;
 constexpr int kWidth = 640;
 
+// The height of the search box in |search_result_page_view_|. It is only for
+// animation.
+constexpr int kSearchBoxHeight = 56;
+
 }  // namespace
 
 AssistantPageView::AssistantPageView(
@@ -73,6 +77,15 @@ gfx::Rect AssistantPageView::GetPageBoundsForState(
   return onscreen_bounds;
 }
 
+gfx::Rect AssistantPageView::GetSearchBoxBounds() const {
+  gfx::Rect rect(AppListPage::GetSearchBoxBounds());
+
+  rect.Offset((rect.width() - kWidth) / 2, 0);
+  rect.set_size(gfx::Size(kWidth, kSearchBoxHeight));
+
+  return rect;
+}
+
 views::View* AssistantPageView::GetFirstFocusableView() {
   return GetFocusManager()->GetNextFocusableView(
       this, GetWidget(), /*reverse=*/false, /*dont_loop=*/false);

ash/app_list/views/assistant/assistant_page_view.h

@@ -34,6 +34,7 @@ class APP_LIST_EXPORT AssistantPageView : public AppListPage {
 
   // AppListPage:
   gfx::Rect GetPageBoundsForState(ash::AppListState state) const override;
+  gfx::Rect GetSearchBoxBounds() const override;
   views::View* GetFirstFocusableView() override;
   views::View* GetLastFocusableView() override;
 

ash/app_list/views/contents_view.cc

@@ -267,7 +267,7 @@ bool ContentsView::IsShowingSearchResults() const {
 }
 
 void ContentsView::ShowEmbeddedAssistantUI(bool show) {
-  int assistant_page =
+  const int assistant_page =
       GetPageIndexForState(ash::AppListState::kStateEmbeddedAssistant);
   DCHECK_GE(assistant_page, 0);
 
@@ -276,7 +276,14 @@ void ContentsView::ShowEmbeddedAssistantUI(bool show) {
   if (show)
     GetPageView(assistant_page)->RequestFocus();
 
-  SetActiveStateInternal(show ? assistant_page : page_before_search_, show,
+  // Embedded Assistant UI can only be transitioned from/to
+  // |search_result_page_view_|.
+  const int search_results_page =
+      GetPageIndexForState(ash::AppListState::kStateSearchResults);
+  DCHECK_GE(search_results_page, 0);
+  GetPageView(search_results_page)->SetVisible(!show);
+  SetActiveStateInternal(show ? assistant_page : search_results_page,
+                         /*show_search_or_assistant_results=*/true,
                          !AppListView::ShortAnimationsForTesting());
 }
 
@@ -499,8 +506,6 @@ bool ContentsView::Back() {
       ShowSearchResults(false);
       break;
     case ash::AppListState::kStateEmbeddedAssistant:
-      GetSearchBoxView()->ClearSearch();
-      GetSearchBoxView()->SetSearchBoxActive(false, ui::ET_UNKNOWN);
       ShowEmbeddedAssistantUI(false);
       break;
     case ash::AppListState::kInvalidState:  // Falls through.