Split TabRestoreService into InMemoryTRS and PersistentTRS

chrome/browser/sessions/persistent_tab_restore_service.cc

Index: chrome/browser/sessions/persistent_tab_restore_service.cc
diff --git a/chrome/browser/sessions/persistent_tab_restore_service.cc b/chrome/browser/sessions/persistent_tab_restore_service.cc
new file mode 100644
index 0000000000000000000000000000000000000000..ca9fd2b8b091da1f3d6eaf6fa49f7f3aecc9fc0c
--- /dev/null
+++ b/chrome/browser/sessions/persistent_tab_restore_service.cc
@@ -0,0 +1,723 @@
+// Copyright (c) 2012 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 "chrome/browser/sessions/persistent_tab_restore_service.h"
+
+#include <cstring>  // memcpy
+#include <vector>
+
+#include "base/basictypes.h"
+#include "base/bind.h"
+#include "base/file_path.h"
+#include "base/logging.h"
+#include "base/memory/scoped_vector.h"
+#include "base/stl_util.h"
+#include "base/time.h"
+#include "chrome/browser/sessions/session_command.h"
+#include "content/public/browser/session_storage_namespace.h"
+
+namespace {
+
+// Only written if the tab is pinned.
+typedef bool PinnedStatePayload;
+
+typedef int32 RestoredEntryPayload;
+
+// Payload used for the start of a tab close. This is the old struct that is
+// used for backwards compat when it comes to reading the session files.
+struct SelectedNavigationInTabPayload {
+  SessionID::id_type id;
+  int32 index;
+};
+
+// Payload used for the start of a window close. This is the old struct that is
+// used for backwards compat when it comes to reading the session files. This
+// struct must be POD, because we memset the contents.
+struct WindowPayload {
+  SessionID::id_type window_id;
+  int32 selected_tab_index;
+  int32 num_tabs;
+};
+
+// Payload used for the start of a window close.  This struct must be POD,
+// because we memset the contents.
+struct WindowPayload2 : WindowPayload {
+  int64 timestamp;
+};
+
+// Payload used for the start of a tab close.
+struct SelectedNavigationInTabPayload2 : SelectedNavigationInTabPayload {
+  int64 timestamp;
+};
+
+// Used to indicate what has loaded.
+enum LoadState {
+  // Indicates we haven't loaded anything.
+  NOT_LOADED           = 1 << 0,
+
+  // Indicates we've asked for the last sessions and tabs but haven't gotten
+  // the result back yet.
+  LOADING              = 1 << 2,
+
+  // Indicates we finished loading the last tabs (but not necessarily the
+  // last session).
+  LOADED_LAST_TABS     = 1 << 3,
+
+  // Indicates we finished loading the last session (but not necessarily the
+  // last tabs).
+  LOADED_LAST_SESSION  = 1 << 4
+};
+
+// Identifier for commands written to file.
+// The ordering in the file is as follows:
+// . When the user closes a tab a command of type
+//   kCommandSelectedNavigationInTab is written identifying the tab and
+//   the selected index, then a kCommandPinnedState command if the tab was
+//   pinned and kCommandSetExtensionAppID if the tab has an app id and
+//   the user agent override if it was using one.  This is
+//   followed by any number of kCommandUpdateTabNavigation commands (1 per
+//   navigation entry).
+// . When the user closes a window a kCommandSelectedNavigationInTab command
+//   is written out and followed by n tab closed sequences (as previoulsy
+//   described).
+// . When the user restores an entry a command of type kCommandRestoredEntry
+//   is written.
+const SessionCommand::id_type kCommandUpdateTabNavigation = 1;
+const SessionCommand::id_type kCommandRestoredEntry = 2;
+const SessionCommand::id_type kCommandWindow = 3;
+const SessionCommand::id_type kCommandSelectedNavigationInTab = 4;
+const SessionCommand::id_type kCommandPinnedState = 5;
+const SessionCommand::id_type kCommandSetExtensionAppID = 6;
+const SessionCommand::id_type kCommandSetWindowAppName = 7;
+const SessionCommand::id_type kCommandSetTabUserAgentOverride = 8;
+
+// Number of entries (not commands) before we clobber the file and write
+// everything.
+const int kEntriesPerReset = 40;
+
+SessionCommand* CreateRestoredEntryCommand(SessionID::id_type entry_id) {
+  RestoredEntryPayload payload = entry_id;
+  SessionCommand* command =
+      new SessionCommand(kCommandRestoredEntry, sizeof(payload));
+  memcpy(command->contents(), &payload, sizeof(payload));
+  return command;
+}
+
+SessionCommand* CreateSelectedNavigationInTabCommand(SessionID::id_type tab_id,
+                                                     int32 index,
+                                                     base::Time timestamp) {
+  SelectedNavigationInTabPayload2 payload;
+  payload.id = tab_id;
+  payload.index = index;
+  payload.timestamp = timestamp.ToInternalValue();
+  SessionCommand* command =
+      new SessionCommand(kCommandSelectedNavigationInTab, sizeof(payload));
+  memcpy(command->contents(), &payload, sizeof(payload));
+  return command;
+}
+
+SessionCommand* CreateWindowCommand(SessionID::id_type id,
+                                    int selected_tab_index,
+                                    int num_tabs,
+                                    base::Time timestamp) {
+  WindowPayload2 payload;
+  // |timestamp| is aligned on a 16 byte boundary, leaving 4 bytes of
+  // uninitialized memory in the struct.
+  memset(&payload, 0, sizeof(payload));
+  payload.window_id = id;
+  payload.selected_tab_index = selected_tab_index;
+  payload.num_tabs = num_tabs;
+  payload.timestamp = timestamp.ToInternalValue();
+
+  SessionCommand* command =
+      new SessionCommand(kCommandWindow, sizeof(payload));
+  memcpy(command->contents(), &payload, sizeof(payload));
+  return command;
+}
+
+
+}  // namespace
+
+PersistentTabRestoreService::PersistentTabRestoreService(
+    Profile* profile,
+    TimeFactory* time_factory)
+    : BaseSessionService(BaseSessionService::TAB_RESTORE, profile,
+                         FilePath()),
+      InMemoryTabRestoreService(profile, time_factory),
+      entries_to_write_(0),
+      entries_written_(0),
+      load_state_(NOT_LOADED) {
+}
+
+PersistentTabRestoreService::~PersistentTabRestoreService() {
+  STLDeleteElements(&staging_entries_);
+}
+
+void PersistentTabRestoreService::Save() {
+  int to_write_count = std::min(entries_to_write_,
+                                static_cast<int>(entries().size()));
+  entries_to_write_ = 0;
+  if (entries_written_ + to_write_count > kEntriesPerReset) {
+    to_write_count = entries().size();
+    set_pending_reset(true);
+  }
+  if (to_write_count) {
+    // Write the to_write_count most recently added entries out. The most
+    // recently added entry is at the front, so we use a reverse iterator to
+    // write in the order the entries were added.
+    Entries::const_reverse_iterator i = entries().rbegin();
+    DCHECK(static_cast<size_t>(to_write_count) <= entries().size());
+    std::advance(i, entries().size() - static_cast<int>(to_write_count));
+    for (; i != entries().rend(); ++i) {
+      Entry* entry = *i;
+      if (entry->type == TAB) {
+        Tab* tab = static_cast<Tab*>(entry);
+        int selected_index = GetSelectedNavigationIndexToPersist(*tab);
+        if (selected_index != -1)
+          ScheduleCommandsForTab(*tab, selected_index);
+      } else {
+        ScheduleCommandsForWindow(*static_cast<Window*>(entry));
+      }
+      entries_written_++;
+    }
+  }
+  if (pending_reset())
+    entries_written_ = 0;
+  BaseSessionService::Save();
+}
+
+bool PersistentTabRestoreService::IsLoaded() const {
+  return !(load_state_ & (NOT_LOADED | LOADING));
+}
+
+void PersistentTabRestoreService::Shutdown() {
+  if (backend())
+    Save();
+}
+
+void PersistentTabRestoreService::OnClearEntries() {
+  const Entries& entries = TabRestoreService::entries();
+  // Mark all the tabs as closed so that we don't attempt to restore them.
+  for (Entries::const_iterator i = entries.begin(); i != entries.end(); ++i)
+    ScheduleCommand(CreateRestoredEntryCommand((*i)->id));
+
+  entries_to_write_ = 0;
+
+  // Schedule a pending reset so that we nuke the file on next write.
+  set_pending_reset(true);
+
+  // Schedule a command, otherwise if there are no pending commands Save does
+  // nothing.
+  ScheduleCommand(CreateRestoredEntryCommand(1));
+}
+
+void PersistentTabRestoreService::OnRestoreEntryById(
+    SessionID::id_type id,
+    Entries::const_iterator entry_iterator) {
+  const Entries& entries = TabRestoreService::entries();
+  size_t index = 0;
+  for (Entries::const_iterator j = entries.begin();
+       j != entry_iterator && j != entries.end();
+       ++j, ++index) {}
+  if (static_cast<int>(index) < entries_to_write_)
+    entries_to_write_--;
+
+  ScheduleCommand(CreateRestoredEntryCommand(id));
+}
+
+void PersistentTabRestoreService::OnAddEntry() {
+  // Start the save timer, when it fires we'll generate the commands.
+  StartSaveTimer();
+  entries_to_write_++;
+}
+
+int PersistentTabRestoreService::GetSelectedNavigationIndexToPersist(
+    const Tab& tab) {
+  const std::vector<TabNavigation>& navigations = tab.navigations;
+  int selected_index = tab.current_navigation_index;
+  int max_index = static_cast<int>(navigations.size());
+
+  // Find the first navigation to persist. We won't persist the selected
+  // navigation if ShouldTrackEntry returns false.
+  while (selected_index >= 0 &&
+         !ShouldTrackEntry(navigations[selected_index].virtual_url())) {
+    selected_index--;
+  }
+
+  if (selected_index != -1)
+    return selected_index;
+
+  // Couldn't find a navigation to persist going back, go forward.
+  selected_index = tab.current_navigation_index + 1;
+  while (selected_index < max_index &&
+         !ShouldTrackEntry(navigations[selected_index].virtual_url())) {
+    selected_index++;
+  }
+
+  return (selected_index == max_index) ? -1 : selected_index;
+}
+
+void PersistentTabRestoreService::ScheduleCommandsForTab(const Tab& tab,
+                                                         int selected_index) {
+  const std::vector<TabNavigation>& navigations = tab.navigations;
+  int max_index = static_cast<int>(navigations.size());
+
+  // Determine the first navigation we'll persist.
+  int valid_count_before_selected = 0;
+  int first_index_to_persist = selected_index;
+  for (int i = selected_index - 1; i >= 0 &&
+       valid_count_before_selected < max_persist_navigation_count; --i) {
+    if (ShouldTrackEntry(navigations[i].virtual_url())) {
+      first_index_to_persist = i;
+      valid_count_before_selected++;
+    }
+  }
+
+  // Write the command that identifies the selected tab.
+  ScheduleCommand(
+      CreateSelectedNavigationInTabCommand(tab.id,
+                                           valid_count_before_selected,
+                                           tab.timestamp));
+
+  if (tab.pinned) {
+    PinnedStatePayload payload = true;
+    SessionCommand* command =
+        new SessionCommand(kCommandPinnedState, sizeof(payload));
+    memcpy(command->contents(), &payload, sizeof(payload));
+    ScheduleCommand(command);
+  }
+
+  if (!tab.extension_app_id.empty()) {
+    ScheduleCommand(
+        CreateSetTabExtensionAppIDCommand(kCommandSetExtensionAppID, tab.id,
+                                          tab.extension_app_id));
+  }
+
+  if (!tab.user_agent_override.empty()) {
+    ScheduleCommand(
+        CreateSetTabUserAgentOverrideCommand(kCommandSetTabUserAgentOverride,
+                                             tab.id, tab.user_agent_override));
+  }
+
+  // Then write the navigations.
+  for (int i = first_index_to_persist, wrote_count = 0;
+       i < max_index && wrote_count < 2 * max_persist_navigation_count; ++i) {
+    if (ShouldTrackEntry(navigations[i].virtual_url())) {
+      ScheduleCommand(
+          CreateUpdateTabNavigationCommand(kCommandUpdateTabNavigation, tab.id,
+                                           navigations[i]));
+    }
+  }
+}
+
+void PersistentTabRestoreService::ScheduleCommandsForWindow(
+    const Window& window) {
+  DCHECK(!window.tabs.empty());
+  int selected_tab = window.selected_tab_index;
+  int valid_tab_count = 0;
+  int real_selected_tab = selected_tab;
+  for (size_t i = 0; i < window.tabs.size(); ++i) {
+    if (GetSelectedNavigationIndexToPersist(window.tabs[i]) != -1) {
+      valid_tab_count++;
+    } else if (static_cast<int>(i) < selected_tab) {
+      real_selected_tab--;
+    }
+  }
+  if (valid_tab_count == 0)
+    return;  // No tabs to persist.
+
+  ScheduleCommand(
+      CreateWindowCommand(window.id,
+                          std::min(real_selected_tab, valid_tab_count - 1),
+                          valid_tab_count,
+                          window.timestamp));
+
+  if (!window.app_name.empty()) {
+    ScheduleCommand(
+        CreateSetWindowAppNameCommand(kCommandSetWindowAppName,
+                                      window.id,
+                                      window.app_name));
+  }
+
+  for (size_t i = 0; i < window.tabs.size(); ++i) {
+    int selected_index = GetSelectedNavigationIndexToPersist(window.tabs[i]);
+    if (selected_index != -1)
+      ScheduleCommandsForTab(window.tabs[i], selected_index);
+  }
+}
+
+void PersistentTabRestoreService::OnGotPreviousSession(
+    Handle handle,
+    std::vector<SessionWindow*>* windows,
+    SessionID::id_type ignored_active_window) {
+  std::vector<Entry*> entries;
+  CreateEntriesFromWindows(windows, &entries);
+  // Previous session tabs go first.
+  staging_entries_.insert(staging_entries_.begin(), entries.begin(),
+                          entries.end());
+  load_state_ |= LOADED_LAST_SESSION;
+  LoadStateChanged();
+}
+
+void PersistentTabRestoreService::OnGotLastSessionCommands(
+    Handle handle,
+    scoped_refptr<InternalGetCommandsRequest> request) {
+  std::vector<Entry*> entries;
+  CreateEntriesFromCommands(request, &entries);
+  // Closed tabs always go to the end.
+  staging_entries_.insert(staging_entries_.end(), entries.begin(),
+                          entries.end());
+  load_state_ |= LOADED_LAST_TABS;
+  LoadStateChanged();
+}
+
+void PersistentTabRestoreService::CreateEntriesFromCommands(
+    scoped_refptr<InternalGetCommandsRequest> request,
+    std::vector<Entry*>* loaded_entries) {
+  if (request->canceled() || entries().size() == kMaxEntries)
+    return;
+
+  std::vector<SessionCommand*>& commands = request->commands;
+  // Iterate through the commands populating entries and id_to_entry.
+  ScopedVector<Entry> entries;
+  IDToEntry id_to_entry;
+  // If non-null we're processing the navigations of this tab.
+  Tab* current_tab = NULL;
+  // If non-null we're processing the tabs of this window.
+  Window* current_window = NULL;
+  // If > 0, we've gotten a window command but not all the tabs yet.
+  int pending_window_tabs = 0;
+  for (std::vector<SessionCommand*>::const_iterator i = commands.begin();
+       i != commands.end(); ++i) {
+    const SessionCommand& command = *(*i);
+    switch (command.id()) {
+      case kCommandRestoredEntry: {
+        if (pending_window_tabs > 0) {
+          // Should never receive a restored command while waiting for all the
+          // tabs in a window.
+          return;
+        }
+
+        current_tab = NULL;
+        current_window = NULL;
+
+        RestoredEntryPayload payload;
+        if (!command.GetPayload(&payload, sizeof(payload)))
+          return;
+        RemoveEntryByID(payload, &id_to_entry, &(entries.get()));
+        break;
+      }
+
+      case kCommandWindow: {
+        WindowPayload2 payload;
+        if (pending_window_tabs > 0) {
+          // Should never receive a window command while waiting for all the
+          // tabs in a window.
+          return;
+        }
+
+        // Try the new payload first
+        if (!command.GetPayload(&payload, sizeof(payload))) {
+          // then the old payload
+          WindowPayload old_payload;
+          if (!command.GetPayload(&old_payload, sizeof(old_payload)))
+            return;
+
+          // Copy the old payload data to the new payload.
+          payload.window_id = old_payload.window_id;
+          payload.selected_tab_index = old_payload.selected_tab_index;
+          payload.num_tabs = old_payload.num_tabs;
+          // Since we don't have a time use time 0 which is used to mark as an
+          // unknown timestamp.
+          payload.timestamp = 0;
+        }
+
+        pending_window_tabs = payload.num_tabs;
+        if (pending_window_tabs <= 0) {
+          // Should always have at least 1 tab. Likely indicates corruption.
+          return;
+        }
+
+        RemoveEntryByID(payload.window_id, &id_to_entry, &(entries.get()));
+
+        current_window = new Window();
+        current_window->selected_tab_index = payload.selected_tab_index;
+        current_window->timestamp =
+            base::Time::FromInternalValue(payload.timestamp);
+        entries.push_back(current_window);
+        id_to_entry[payload.window_id] = current_window;
+        break;
+      }
+
+      case kCommandSelectedNavigationInTab: {
+        SelectedNavigationInTabPayload2 payload;
+        if (!command.GetPayload(&payload, sizeof(payload))) {
+          SelectedNavigationInTabPayload old_payload;
+          if (!command.GetPayload(&old_payload, sizeof(old_payload)))
+            return;
+          payload.id = old_payload.id;
+          payload.index = old_payload.index;
+          // Since we don't have a time use time 0 which is used to mark as an
+          // unknown timestamp.
+          payload.timestamp = 0;
+        }
+
+        if (pending_window_tabs > 0) {
+          if (!current_window) {
+            // We should have created a window already.
+            NOTREACHED();
+            return;
+          }
+          current_window->tabs.resize(current_window->tabs.size() + 1);
+          current_tab = &(current_window->tabs.back());
+          if (--pending_window_tabs == 0)
+            current_window = NULL;
+        } else {
+          RemoveEntryByID(payload.id, &id_to_entry, &(entries.get()));
+          current_tab = new Tab();
+          id_to_entry[payload.id] = current_tab;
+          current_tab->timestamp =
+              base::Time::FromInternalValue(payload.timestamp);
+          entries.push_back(current_tab);
+        }
+        current_tab->current_navigation_index = payload.index;
+        break;
+      }
+
+      case kCommandUpdateTabNavigation: {
+        if (!current_tab) {
+          // Should be in a tab when we get this.
+          return;
+        }
+        current_tab->navigations.resize(current_tab->navigations.size() + 1);
+        SessionID::id_type tab_id;
+        if (!RestoreUpdateTabNavigationCommand(
+            command, &current_tab->navigations.back(), &tab_id)) {
+          return;
+        }
+        break;
+      }
+
+      case kCommandPinnedState: {
+        if (!current_tab) {
+          // Should be in a tab when we get this.
+          return;
+        }
+        // NOTE: payload doesn't matter. kCommandPinnedState is only written if
+        // tab is pinned.
+        current_tab->pinned = true;
+        break;
+      }
+
+      case kCommandSetWindowAppName: {
+        if (!current_window) {
+          // We should have created a window already.
+          NOTREACHED();
+          return;
+        }
+
+        SessionID::id_type window_id;
+        std::string app_name;
+        if (!RestoreSetWindowAppNameCommand(command, &window_id, &app_name))
+          return;
+
+        current_window->app_name.swap(app_name);
+        break;
+      }
+
+      case kCommandSetExtensionAppID: {
+        if (!current_tab) {
+          // Should be in a tab when we get this.
+          return;
+        }
+        SessionID::id_type tab_id;
+        std::string extension_app_id;
+        if (!RestoreSetTabExtensionAppIDCommand(command, &tab_id,
+                                                &extension_app_id)) {
+          return;
+        }
+        current_tab->extension_app_id.swap(extension_app_id);
+        break;
+      }
+
+      case kCommandSetTabUserAgentOverride: {
+        if (!current_tab) {
+          // Should be in a tab when we get this.
+          return;
+        }
+        SessionID::id_type tab_id;
+        std::string user_agent_override;
+        if (!RestoreSetTabUserAgentOverrideCommand(command, &tab_id,
+                                                   &user_agent_override)) {
+          return;
+        }
+        current_tab->user_agent_override.swap(user_agent_override);
+        break;
+      }
+
+      default:
+        // Unknown type, usually indicates corruption of file. Ignore it.
+        return;
+    }
+  }
+
+  // If there was corruption some of the entries won't be valid.
+  ValidateAndDeleteEmptyEntries(&(entries.get()));
+
+  loaded_entries->swap(entries.get());
+}
+
+void PersistentTabRestoreService::CreateEntriesFromWindows(
+    std::vector<SessionWindow*>* windows,
+    std::vector<Entry*>* entries) {
+  for (size_t i = 0; i < windows->size(); ++i) {
+    scoped_ptr<Window> window(new Window());
+    if (ConvertSessionWindowToWindow((*windows)[i], window.get()))
+      entries->push_back(window.release());
+  }
+}
+
+void PersistentTabRestoreService::RemoveEntryByID(
+    SessionID::id_type id,
+    IDToEntry* id_to_entry,
+    std::vector<TabRestoreService::Entry*>* entries) {
+  // Look for the entry in the map. If it is present, erase it from both
+  // collections and return.
+  IDToEntry::iterator i = id_to_entry->find(id);
+  if (i != id_to_entry->end()) {
+    entries->erase(std::find(entries->begin(), entries->end(), i->second));
+    delete i->second;
+    id_to_entry->erase(i);
+    return;
+  }
+
+  // Otherwise, loop over all items in the map and see if any of the Windows
+  // have Tabs with the |id|.
+  for (IDToEntry::iterator i = id_to_entry->begin(); i != id_to_entry->end();
+       ++i) {
+    if (i->second->type == TabRestoreService::WINDOW) {
+      TabRestoreService::Window* window =
+          static_cast<TabRestoreService::Window*>(i->second);
+      std::vector<TabRestoreService::Tab>::iterator j = window->tabs.begin();
+      for ( ; j != window->tabs.end(); ++j) {
+        // If the ID matches one of this window's tabs, remove it from the list.
+        if ((*j).id == id) {
+          window->tabs.erase(j);
+          return;
+        }
+      }
+    }
+  }
+}
+
+// static
+void PersistentTabRestoreService::ValidateAndDeleteEmptyEntries(
+    std::vector<Entry*>* entries) {
+  std::vector<Entry*> valid_entries;
+  std::vector<Entry*> invalid_entries;
+
+  // Iterate from the back so that we keep the most recently closed entries.
+  for (std::vector<Entry*>::reverse_iterator i = entries->rbegin();
+       i != entries->rend(); ++i) {
+    if (ValidateEntry(*i))
+      valid_entries.push_back(*i);
+    else
+      invalid_entries.push_back(*i);
+  }
+  // NOTE: at this point the entries are ordered with newest at the front.
+  entries->swap(valid_entries);
+
+  // Delete the remaining entries.
+  STLDeleteElements(&invalid_entries);
+}
+
+void PersistentTabRestoreService::LoadTabsFromLastSession() {
+  if (load_state_ != NOT_LOADED || entries().size() == kMaxEntries)
+    return;
+
+#if !defined(ENABLE_SESSION_SERVICE)
+  // If sessions are not stored in the SessionService, default to
+  // |LOADED_LAST_SESSION| state.
+  load_state_ = LOADING | LOADED_LAST_SESSION;
+#else
+  load_state_ = LOADING;
+
+  SessionService* session_service =
+      SessionServiceFactory::GetForProfile(profile_);
+  Profile::ExitType exit_type = profile()->GetLastSessionExitType();
+  if (!profile()->restored_last_session() && session_service &&
+      (exit_type == Profile::EXIT_CRASHED ||
+       exit_type == Profile::EXIT_SESSION_ENDED)) {
+    // The previous session crashed and wasn't restored, or was a forced
+    // shutdown. Both of which won't have notified us of the browser close so
+    // that we need to load the windows from session service (which will have
+    // saved them).
+    session_service->GetLastSession(
+        &crash_consumer_,
+        base::Bind(&PersistentTabRestoreService::OnGotPreviousSession,
+                   base::Unretained(this)));
+  } else {
+    load_state_ |= LOADED_LAST_SESSION;
+  }
+#endif
+
+  // Request the tabs closed in the last session. If the last session crashed,
+  // this won't contain the tabs/window that were open at the point of the
+  // crash (the call to GetLastSession above requests those).
+  ScheduleGetLastSessionCommands(
+      new InternalGetCommandsRequest(
+          base::Bind(&PersistentTabRestoreService::OnGotLastSessionCommands,
+                     base::Unretained(this))),
+      &load_consumer_);
+}
+
+void PersistentTabRestoreService::LoadStateChanged() {
+  if ((load_state_ & (LOADED_LAST_TABS | LOADED_LAST_SESSION)) !=
+      (LOADED_LAST_TABS | LOADED_LAST_SESSION)) {
+    // Still waiting on previous session or previous tabs.
+    return;
+  }
+
+  // We're done loading.
+  load_state_ ^= LOADING;
+
+  const size_t entries_size = entries().size();
+  if (staging_entries_.empty() || entries_size >= kMaxEntries) {
+    STLDeleteElements(&staging_entries_);
+    return;
+  }
+
+  if (staging_entries_.size() + entries_size > kMaxEntries) {
+    // If we add all the staged entries we'll end up with more than
+    // kMaxEntries. Delete entries such that we only end up with
+    // at most kMaxEntries.
+    int surplus = kMaxEntries - entries_size;
+    CHECK_LE(0, surplus);
+    CHECK_GE(static_cast<int>(staging_entries_.size()), surplus);
+    STLDeleteContainerPointers(
+        staging_entries_.begin() + (kMaxEntries - entries_size),
+        staging_entries_.end());
+    staging_entries_.erase(
+        staging_entries_.begin() + (kMaxEntries - entries_size),
+        staging_entries_.end());
+  }
+
+  // And add them.
+  for (size_t i = 0; i < staging_entries_.size(); ++i) {
+    staging_entries_[i]->from_last_session = true;
+    AddEntry(staging_entries_[i], false, false);
+  }
+
+  // AddEntry takes ownership of the entry, need to clear out entries so that
+  // it doesn't delete them.
+  staging_entries_.clear();
+
+  // Make it so we rewrite all the tabs. We need to do this otherwise we won't
+  // correctly write out the entries when Save is invoked (Save starts from
+  // the front, not the end and we just added the entries to the end).
+  entries_to_write_ = staging_entries_.size();
+
+  PruneEntries();
+  NotifyTabsChanged();
+}