Revert "Remove HoldingSpacePresenter."

This reverts commit 57e175db.

Reason for revert: Seems to break presubmit due to missing OWNERS file

Original change's description:
> Remove HoldingSpacePresenter.
> 
> No longer needed given evolution of feature requirements.
> 
> Bug: 1112469
> Change-Id: Ic31d2a02fcc624ddc101447f68089cfff9bd2660
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2377535
> Reviewed-by: Toni Baržić <tbarzic@chromium.org>
> Commit-Queue: David Black <dmblack@google.com>
> Cr-Commit-Position: refs/heads/master@{#801857}

TBR=tbarzic@chromium.org,dmblack@google.com

Change-Id: I6c7b1254e9af0ae662b8afc7d37db50dff5c312d
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: 1112469
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2377654Reviewed-by: David Black <dmblack@google.com>
Commit-Queue: David Black <dmblack@google.com>
Cr-Commit-Position: refs/heads/master@{#801885}

ash/BUILD.gn

@@ -443,6 +443,8 @@ component("ash") {
     "highlighter/highlighter_result_view.h",
     "highlighter/highlighter_view.cc",
     "highlighter/highlighter_view.h",
+    "holding_space/holding_space_presenter.cc",
+    "holding_space/holding_space_presenter.h",
     "home_screen/drag_window_from_shelf_controller.cc",
     "home_screen/drag_window_from_shelf_controller.h",
     "home_screen/home_launcher_gesture_handler.cc",
@@ -1885,6 +1887,7 @@ test("ash_unittests") {
     "frame/non_client_frame_view_ash_unittest.cc",
     "highlighter/highlighter_controller_unittest.cc",
     "highlighter/highlighter_gesture_util_unittest.cc",
+    "holding_space/holding_space_presenter_unittest.cc",
     "home_screen/drag_window_from_shelf_controller_test_api.cc",
     "home_screen/drag_window_from_shelf_controller_test_api.h",
     "home_screen/drag_window_from_shelf_controller_unittest.cc",

ash/holding_space/DIR_METADATA

+# Metadata information for this directory.
+#
+# For more information on DIR_METADATA files, see:
+#   https://source.chromium.org/chromium/infra/infra/+/master:go/src/infra/tools/dirmd/README.md
+#
+# For the schema of this file, see Metadata message:
+#   https://source.chromium.org/chromium/infra/infra/+/master:go/src/infra/tools/dirmd/proto/dir_metadata.proto
+
+monorail {
+  component: "UI>Shell>HoldingSpace"
+}
\ No newline at end of file

ash/holding_space/OWNERS

+tbarzic@chromium.org
+newcomer@chromium.org

ash/holding_space/holding_space_presenter.cc

+// Copyright 2020 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+//
+#include "ash/holding_space/holding_space_presenter.h"
+
+#include "ash/public/cpp/holding_space/holding_space_item.h"
+#include "base/stl_util.h"
+
+namespace ash {
+
+HoldingSpacePresenter::HoldingSpacePresenter() {
+  HoldingSpaceController* const controller = HoldingSpaceController::Get();
+  controller_observer_.Add(controller);
+  if (controller->model())
+    HandleNewModel(controller->model());
+}
+
+HoldingSpacePresenter::~HoldingSpacePresenter() = default;
+
+void HoldingSpacePresenter::OnHoldingSpaceModelAttached(
+    HoldingSpaceModel* model) {
+  HandleNewModel(model);
+}
+
+void HoldingSpacePresenter::OnHoldingSpaceModelDetached(
+    HoldingSpaceModel* model) {
+  model_observer_.Remove(model);
+  item_ids_.clear();
+}
+
+void HoldingSpacePresenter::OnHoldingSpaceItemAdded(
+    const HoldingSpaceItem* item) {
+  item_ids_[item->type()].push_back(item->id());
+}
+
+void HoldingSpacePresenter::OnHoldingSpaceItemRemoved(
+    const HoldingSpaceItem* item) {
+  base::Erase(item_ids_[item->type()], item->id());
+}
+
+const std::vector<std::string>& HoldingSpacePresenter::GetItemIds(
+    HoldingSpaceItem::Type type) const {
+  const auto& item_list_it = item_ids_.find(type);
+  if (item_list_it == item_ids_.end()) {
+    static std::vector<std::string> empty_list;
+    return empty_list;
+  }
+  return item_list_it->second;
+}
+
+void HoldingSpacePresenter::HandleNewModel(HoldingSpaceModel* model) {
+  model_observer_.Add(model);
+
+  for (auto& item : model->items())
+    item_ids_[item->type()].push_back(item->id());
+}
+
+}  // namespace ash

ash/holding_space/holding_space_presenter.h

+// Copyright 2020 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+//
+#ifndef ASH_HOLDING_SPACE_HOLDING_SPACE_PRESENTER_H_
+#define ASH_HOLDING_SPACE_HOLDING_SPACE_PRESENTER_H_
+
+#include <string>
+#include <vector>
+
+#include "ash/ash_export.h"
+#include "ash/public/cpp/holding_space/holding_space_controller.h"
+#include "ash/public/cpp/holding_space/holding_space_controller_observer.h"
+#include "ash/public/cpp/holding_space/holding_space_item.h"
+#include "ash/public/cpp/holding_space/holding_space_model.h"
+#include "ash/public/cpp/holding_space/holding_space_model_observer.h"
+#include "base/containers/flat_map.h"
+#include "base/scoped_observer.h"
+
+namespace ash {
+
+class HoldingSpaceItem;
+
+// Manages the temporary holding space UI for a root window.
+// The main job of the class is
+// *   to observe the holding space model and update item representations in the
+//     holding space UI.
+// *   to handle user actions within the holding space UI, and updates the
+//     holding space model accordingly.
+// NOTE: Currently this class only tracks the list of items within the active
+// holding space model.
+class ASH_EXPORT HoldingSpacePresenter : public HoldingSpaceControllerObserver,
+                                         public HoldingSpaceModelObserver {
+ public:
+  HoldingSpacePresenter();
+  HoldingSpacePresenter(const HoldingSpacePresenter& other) = delete;
+  HoldingSpacePresenter& operator=(const HoldingSpacePresenter& other) = delete;
+  ~HoldingSpacePresenter() override;
+
+  // HoldingSpaceControllerObserver:
+  void OnHoldingSpaceModelAttached(HoldingSpaceModel* model) override;
+  void OnHoldingSpaceModelDetached(HoldingSpaceModel* model) override;
+
+  // HoldingSpaceModelObserver:
+  void OnHoldingSpaceItemAdded(const HoldingSpaceItem* item) override;
+  void OnHoldingSpaceItemRemoved(const HoldingSpaceItem* item) override;
+
+  const std::vector<std::string>& GetItemIds(HoldingSpaceItem::Type type) const;
+
+ private:
+  // Handles the items from the model, and starts observing the model.
+  void HandleNewModel(HoldingSpaceModel* model);
+
+  // IDs of items in the active holding space model, as observed by the holding
+  // space presenter.
+  base::flat_map<HoldingSpaceItem::Type, std::vector<std::string>> item_ids_;
+
+  ScopedObserver<HoldingSpaceController, HoldingSpaceControllerObserver>
+      controller_observer_{this};
+  ScopedObserver<HoldingSpaceModel, HoldingSpaceModelObserver> model_observer_{
+      this};
+};
+
+}  // namespace ash
+
+#endif  // ASH_HOLDING_SPACE_HOLDING_SPACE_PRESENTER_H_