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

chrome/browser/android/offline_pages/offline_page_bridge.cc

Index: chrome/browser/android/offline_pages/offline_page_bridge.cc
diff --git a/chrome/browser/android/offline_pages/offline_page_bridge.cc b/chrome/browser/android/offline_pages/offline_page_bridge.cc
index 2661b852181505c30741a3229c6ffd8d9c8515f9..99304607882d25de4125909ea391eab0899780a0 100644
--- a/chrome/browser/android/offline_pages/offline_page_bridge.cc
+++ b/chrome/browser/android/offline_pages/offline_page_bridge.cc
@@ -28,6 +28,7 @@
 #include "components/offline_pages/core/offline_page_feature.h"
 #include "components/offline_pages/core/offline_page_item.h"
 #include "components/offline_pages/core/offline_page_model.h"
+#include "components/offline_pages/core/recent_tabs/recent_tabs_ui_adapter_delegate.h"
 #include "components/offline_pages/core/request_header/offline_page_header.h"
 #include "content/public/browser/browser_context.h"
 #include "content/public/browser/web_contents.h"
@@ -569,6 +570,32 @@ void OfflinePageBridge::RemoveRequestsFromQueue(
       request_ids, base::Bind(&OnRemoveRequestsDone, j_callback_ref));
 }
 
+void OfflinePageBridge::RegisterRecentTab(JNIEnv* env,
+                                          const JavaParamRef<jobject>& obj,
+                                          int tab_id) {
+  RequestCoordinator* request_coordinator =
+      RequestCoordinatorFactory::GetForBrowserContext(browser_context_);
+
+  RecentTabsUIAdapterDelegate* ui_adapter_delegate =
+      RecentTabsUIAdapterDelegate::FromDownloadUIAdapter(
+          RecentTabsUIAdapterDelegate::GetOrCreateRecentTabsUIAdapter(
+              offline_page_model_, request_coordinator));
+  ui_adapter_delegate->RegisterTab(tab_id);
+}
+
+void OfflinePageBridge::UnregisterRecentTab(JNIEnv* env,
+                                            const JavaParamRef<jobject>& obj,
+                                            int tab_id) {
+  RequestCoordinator* request_coordinator =
+      RequestCoordinatorFactory::GetForBrowserContext(browser_context_);
+
+  RecentTabsUIAdapterDelegate* ui_adapter_delegate =
+      RecentTabsUIAdapterDelegate::FromDownloadUIAdapter(
+          RecentTabsUIAdapterDelegate::GetOrCreateRecentTabsUIAdapter(
+              offline_page_model_, request_coordinator));
+  ui_adapter_delegate->UnregisterTab(tab_id);
+}
+
 void OfflinePageBridge::NotifyIfDoneLoading() const {
   if (!offline_page_model_->is_loaded())
     return;