Scope SearchResultImageViewDelegate to image list

Instead of using a global SearchResultImageViewDelegate instance in
SearchResultImageViews, scope the delegate to an
SearchResultImageListView, and pass it to SearchResultImageViews in
their constructors. Using a global SearchResultImageViewDelegate had an
invalid assumption that at most one instance could exist at the time -
this did not take into account that both bubble and tablet mode launcher
have their own SearchResultImageListView, and thus their own
SearchResultImageViewDelegate.

Change-Id: I4ed0257262a792679e130ca08d83a903b237b229
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5181716
Reviewed-by: Wen-Chien Wang <wcwang@chromium.org>
Commit-Queue: Toni Barzic <tbarzic@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1245050}

diff --git a/ash/app_list/views/search_result_image_list_view.cc b/ash/app_list/views/search_result_image_list_view.cc
index 03765dc9..767034e 100644
--- a/ash/app_list/views/search_result_image_list_view.cc
+++ b/ash/app_list/views/search_result_image_list_view.cc

@@ -118,7 +118,7 @@
   for (size_t i = 0;
        i < SharedAppListConfig::instance().image_search_max_results(); ++i) {
     auto* image_view = image_view_container_->AddChildView(
-        std::make_unique<SearchResultImageView>(/*index=*/1, this));
+        std::make_unique<SearchResultImageView>(/*index=*/1, this, &delegate_));
     image_view->SetPaintToLayer();
     image_view->layer()->SetFillsBoundsOpaquely(false);
     image_views_.push_back(image_view);

diff --git a/ash/app_list/views/search_result_image_list_view.h b/ash/app_list/views/search_result_image_list_view.h
index 590670e..13cd2f5 100644
--- a/ash/app_list/views/search_result_image_list_view.h
+++ b/ash/app_list/views/search_result_image_list_view.h

@@ -66,9 +66,8 @@
   views::View* GetTitleLabel() override;
   std::vector<views::View*> GetViewsToAnimate() override;
 
-  // The singleton delegate for search result image views that implements
-  // support for context menu and drag-and-drop operations. This delegate needs
-  // to be a singleton to support multi-selection which requires a shared state.
+  // Delegate for search result image views that implements support for context
+  // menu and drag-and-drop operations.
   SearchResultImageViewDelegate delegate_;
 
   // Owned by views hierarchy.

diff --git a/ash/app_list/views/search_result_image_view.cc b/ash/app_list/views/search_result_image_view.cc
index ef87dd09..e1bf234b 100644
--- a/ash/app_list/views/search_result_image_view.cc
+++ b/ash/app_list/views/search_result_image_view.cc

@@ -81,7 +81,8 @@
 
 SearchResultImageView::SearchResultImageView(
     int index,
-    SearchResultImageListView* list_view)
+    SearchResultImageListView* list_view,
+    SearchResultImageViewDelegate* image_view_delegate)
     : index_(index), list_view_(list_view) {
   SetLayoutManager(std::make_unique<views::FillLayout>());
   result_image_ = AddChildView(std::make_unique<ImagePreviewView>());
@@ -106,7 +107,7 @@
   SetCallback(base::BindRepeating(&SearchResultImageView::OnImageViewPressed,
                                   base::Unretained(this)));
 
-  set_drag_controller(SearchResultImageViewDelegate::Get());
+  set_drag_controller(image_view_delegate);
 }
 
 void SearchResultImageView::OnImageViewPressed(const ui::Event& event) {

diff --git a/ash/app_list/views/search_result_image_view.h b/ash/app_list/views/search_result_image_view.h
index 7a06a6b..d46683b 100644
--- a/ash/app_list/views/search_result_image_view.h
+++ b/ash/app_list/views/search_result_image_view.h

@@ -17,12 +17,15 @@
 namespace ash {
 class PulsingBlockView;
 class SearchResultImageListView;
+class SearchResultImageViewDelegate;
 
 // Displays a search result in the form of an unlabeled image.
 class ASH_EXPORT SearchResultImageView : public SearchResultBaseView {
  public:
   METADATA_HEADER(SearchResultImageView);
-  SearchResultImageView(int index, SearchResultImageListView* list_view);
+  SearchResultImageView(int index,
+                        SearchResultImageListView* list_view,
+                        SearchResultImageViewDelegate* image_view_delegate);
   SearchResultImageView(const SearchResultImageView&) = delete;
   SearchResultImageView& operator=(const SearchResultImageView&) = delete;
   ~SearchResultImageView() override;

diff --git a/ash/app_list/views/search_result_image_view_delegate.cc b/ash/app_list/views/search_result_image_view_delegate.cc
index 82816cf..1fcf14b 100644
--- a/ash/app_list/views/search_result_image_view_delegate.cc
+++ b/ash/app_list/views/search_result_image_view_delegate.cc

@@ -14,24 +14,10 @@
 #include "ui/views/view_utils.h"
 
 namespace ash {
-namespace {
-SearchResultImageViewDelegate* g_instance = nullptr;
-}  // namespace
 
-// static
-SearchResultImageViewDelegate* SearchResultImageViewDelegate::Get() {
-  return g_instance;
-}
+SearchResultImageViewDelegate::SearchResultImageViewDelegate() = default;
 
-SearchResultImageViewDelegate::SearchResultImageViewDelegate() {
-  DCHECK_EQ(nullptr, g_instance);
-  g_instance = this;
-}
-
-SearchResultImageViewDelegate::~SearchResultImageViewDelegate() {
-  DCHECK_EQ(g_instance, this);
-  g_instance = nullptr;
-}
+SearchResultImageViewDelegate::~SearchResultImageViewDelegate() = default;
 
 bool SearchResultImageViewDelegate::CanStartDragForView(
     views::View* sender,

diff --git a/ash/app_list/views/search_result_image_view_delegate.h b/ash/app_list/views/search_result_image_view_delegate.h
index fd394f79..fe77eca 100644
--- a/ash/app_list/views/search_result_image_view_delegate.h
+++ b/ash/app_list/views/search_result_image_view_delegate.h

@@ -13,15 +13,9 @@
 namespace ash {
 class SearchResultImageView;
 
-// A delegate for `SearchResultImageView` which implements drag and drop. Only a
-// single delegate instance exists at a time and is shared by all existing
-// search result image views in order to support multiselection which requires a
-// shared state.
+// A delegate for `SearchResultImageView` which implements drag and drop.
 class ASH_EXPORT SearchResultImageViewDelegate : public views::DragController {
  public:
-  // Returns the singleton instance.
-  static SearchResultImageViewDelegate* Get();
-
   SearchResultImageViewDelegate();
   SearchResultImageViewDelegate(const SearchResultImageViewDelegate&) = delete;
   SearchResultImageViewDelegate& operator=(