Only show Last N Pages in the UI when the corresponding tab is visible.

components/offline_pages/core/recent_tabs/recent_tabs_ui_adapter_delegate.cc

Index: components/offline_pages/core/recent_tabs/recent_tabs_ui_adapter_delegate.cc
diff --git a/components/offline_pages/core/recent_tabs/recent_tabs_ui_adapter_delegate.cc b/components/offline_pages/core/recent_tabs/recent_tabs_ui_adapter_delegate.cc
new file mode 100644
index 0000000000000000000000000000000000000000..257aa7faa172a177d3b7bd7b7ef1511655d7a7c6
--- /dev/null
+++ b/components/offline_pages/core/recent_tabs/recent_tabs_ui_adapter_delegate.cc
@@ -0,0 +1,96 @@
+// Copyright 2016 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 "components/offline_pages/core/recent_tabs/recent_tabs_ui_adapter_delegate.h"
+
+#include "base/bind.h"
+#include "base/threading/thread_task_runner_handle.h"
+#include "components/offline_pages/core/client_policy_controller.h"
+#include "components/offline_pages/core/offline_page_model.h"
+
+namespace offline_pages {
+
+namespace {
+const char kRecentTabsUIAdapterKey[] = "recent-tabs-download-ui-adapter";
+

[Dmitry Titov, 2017/02/14 23:01:03]

extra empty line

[dewittj, 2017/02/15 19:49:45]

Done.

+}  // namespace
+
+RecentTabsUIAdapterDelegate::RecentTabsUIAdapterDelegate(
+    OfflinePageModel* model)
+    : model_(model) {}
+
+RecentTabsUIAdapterDelegate::~RecentTabsUIAdapterDelegate() = default;
+
+offline_pages::DownloadUIAdapter*
+RecentTabsUIAdapterDelegate::GetOrCreateRecentTabsUIAdapter(
+    offline_pages::OfflinePageModel* offline_page_model,
+    offline_pages::RequestCoordinator* request_coordinator) {
+  offline_pages::DownloadUIAdapter* recent_tabs_ui_adapter =
+      static_cast<DownloadUIAdapter*>(
+          offline_page_model->GetUserData(kRecentTabsUIAdapterKey));
+
+  if (!recent_tabs_ui_adapter) {
+    auto delegate =
+        base::MakeUnique<RecentTabsUIAdapterDelegate>(offline_page_model);
+    RecentTabsUIAdapterDelegate* delegate_ptr = delegate.get();

[Dmitry Titov, 2017/02/14 23:01:03]

This looks like a very painful hook up.
Since you already add DownloadUIAdapter::delegate(), you don't seem to need
delegate_ptr which is used after std::move(delegate)...

[dewittj, 2017/02/15 19:49:45]

delegate() is not the right type exactly, so that strategy would require a
static_cast.  What do you think of this alternate approach?

+    recent_tabs_ui_adapter = new DownloadUIAdapter(
+        offline_page_model, request_coordinator, std::move(delegate));
+    delegate_ptr->set_ui_adapter(recent_tabs_ui_adapter);
+    offline_page_model->SetUserData(kRecentTabsUIAdapterKey,
+                                    recent_tabs_ui_adapter);
+  }
+
+  return recent_tabs_ui_adapter;
+}
+
+// static
+RecentTabsUIAdapterDelegate* RecentTabsUIAdapterDelegate::FromDownloadUIAdapter(
+    DownloadUIAdapter* ui_adapter) {
+  return static_cast<RecentTabsUIAdapterDelegate*>(ui_adapter->delegate());
+}
+
+// static
+int RecentTabsUIAdapterDelegate::TabIdFromClientId(const ClientId& client_id) {
+  int tab_id = 0;
+  bool convert_result = base::StringToInt(client_id.id, &tab_id);
+  DCHECK(convert_result);
+  return tab_id;
+}
+
+bool RecentTabsUIAdapterDelegate::IsVisibleInUI(const ClientId& client_id) {
+  return IsRecentTab(client_id);
+}
+
+bool RecentTabsUIAdapterDelegate::IsTemporarilyHiddenInUI(
+    const ClientId& client_id) {
+  return active_tabs_.count(TabIdFromClientId(client_id)) == 0;
+}
+
+void RecentTabsUIAdapterDelegate::RegisterTab(int tab_id) {
+  DCHECK(ui_adapter_);
+  if (active_tabs_.count(tab_id) > 0)
+    return;
+  active_tabs_.insert(tab_id);
+  ui_adapter_->TemporaryHiddenStatusChanged(ClientIdFromTabId(tab_id));
+}
+
+void RecentTabsUIAdapterDelegate::UnregisterTab(int tab_id) {
+  DCHECK(ui_adapter_);
+  if (active_tabs_.count(tab_id) == 0)
+    return;
+  active_tabs_.erase(tab_id);
+  ui_adapter_->TemporaryHiddenStatusChanged(ClientIdFromTabId(tab_id));
+}
+
+// static
+ClientId RecentTabsUIAdapterDelegate::ClientIdFromTabId(int tab_id) {
+  return ClientId(kLastNNamespace, base::IntToString(tab_id));
+}
+
+bool RecentTabsUIAdapterDelegate::IsRecentTab(const ClientId& page) {
+  return model_->GetPolicyController()->IsShownAsRecentlyVisitedSite(
+      page.name_space);
+}
+
+}  // namespace offline_pages