Makes the tab restore service persist closed tabs/windows to disk and

reload them when asked.

Sorry for largish looking change. It's made big by refactoring common
code between TabRestoreService and SessionService into a common
superclass. At the same time I removed some dead code and shuffled the
session related classes into a single directory for easier perusal.

BUG=384
TEST=close the browser, start the browser and make sure the new tab
     page shows closed windows/tabs from the previous session.

Review URL: http://codereview.chromium.org/13152

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@6490 0039d316-1c4b-4281-b951-d872f2087c98

1 files changed, 1120 insertions, 0 deletions

diff --git a/chrome/browser/sessions/session_service.cc b/chrome/browser/sessions/session_service.cc
new file mode 100644
index 0000000..6016651
--- /dev/null
+++ b/chrome/browser/sessions/session_service.cc
@@ -0,0 +1,1120 @@
+// Copyright (c) 2006-2008 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/session_service.h"
+
+#include <limits>
+
+#include "base/file_util.h"
+#include "base/message_loop.h"
+#include "base/pickle.h"
+#include "base/thread.h"
+#include "chrome/browser/browser_init.h"
+#include "chrome/browser/browser_list.h"
+#include "chrome/browser/browser_process.h"
+#include "chrome/browser/browser_window.h"
+#include "chrome/browser/navigation_controller.h"
+#include "chrome/browser/navigation_entry.h"
+#include "chrome/browser/profile.h"
+#include "chrome/browser/session_startup_pref.h"
+#include "chrome/browser/sessions/session_backend.h"
+#include "chrome/browser/sessions/session_restore.h"
+#include "chrome/browser/sessions/session_types.h"
+#include "chrome/browser/tab_contents.h"
+#include "chrome/common/notification_details.h"
+#include "chrome/common/notification_service.h"
+#include "chrome/common/notification_types.h"
+#include "chrome/common/scoped_vector.h"
+#include "chrome/common/win_util.h"
+
+using base::Time;
+
+// Identifier for commands written to file.
+static const SessionCommand::id_type kCommandSetTabWindow = 0;
+// kCommandSetWindowBounds is no longer used (it's superseded by
+// kCommandSetWindowBounds2). I leave it here to document what it was.
+// static const SessionCommand::id_type kCommandSetWindowBounds = 1;
+static const SessionCommand::id_type kCommandSetTabIndexInWindow = 2;
+static const SessionCommand::id_type kCommandTabClosed = 3;
+static const SessionCommand::id_type kCommandWindowClosed = 4;
+static const SessionCommand::id_type
+    kCommandTabNavigationPathPrunedFromBack = 5;
+static const SessionCommand::id_type kCommandUpdateTabNavigation = 6;
+static const SessionCommand::id_type kCommandSetSelectedNavigationIndex = 7;
+static const SessionCommand::id_type kCommandSetSelectedTabInIndex = 8;
+static const SessionCommand::id_type kCommandSetWindowType = 9;
+static const SessionCommand::id_type kCommandSetWindowBounds2 = 10;
+static const SessionCommand::id_type
+    kCommandTabNavigationPathPrunedFromFront = 11;
+
+// Every kWritesPerReset commands triggers recreating the file.
+static const int kWritesPerReset = 250;
+
+namespace {
+
+// The callback from GetLastSession is internally routed to SessionService
+// first and then the caller. This is done so that the SessionWindows can be
+// recreated from the SessionCommands and the SessionWindows passed to the
+// caller. The following class is used for this.
+class InternalLastSessionRequest :
+    public BaseSessionService::InternalGetCommandsRequest {
+ public:
+  InternalLastSessionRequest(
+      CallbackType* callback,
+      SessionService::LastSessionCallback* real_callback)
+      : BaseSessionService::InternalGetCommandsRequest(callback),
+        real_callback(real_callback) {
+  }
+
+  // The callback supplied to GetLastSession.
+  scoped_ptr<SessionService::LastSessionCallback> real_callback;
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(InternalLastSessionRequest);
+};
+
+// Various payload structures.
+struct ClosedPayload {
+  SessionID::id_type id;
+  int64 close_time;
+};
+
+struct WindowBoundsPayload2 {
+  SessionID::id_type window_id;
+  int32 x;
+  int32 y;
+  int32 w;
+  int32 h;
+  bool is_maximized;
+};
+
+struct IDAndIndexPayload {
+  SessionID::id_type id;
+  int32 index;
+};
+
+typedef IDAndIndexPayload TabIndexInWindowPayload;
+
+typedef IDAndIndexPayload TabNavigationPathPrunedFromBackPayload;
+
+typedef IDAndIndexPayload SelectedNavigationIndexPayload;
+
+typedef IDAndIndexPayload SelectedTabInIndexPayload;
+
+typedef IDAndIndexPayload WindowTypePayload;
+
+typedef IDAndIndexPayload TabNavigationPathPrunedFromFrontPayload;
+
+}  // namespace
+
+// SessionService -------------------------------------------------------------
+
+SessionService::SessionService(Profile* profile)
+    : BaseSessionService(SESSION_RESTORE, profile, std::wstring()),
+      has_open_tabbed_browsers_(false),
+      move_on_new_browser_(false) {
+  Init();
+}
+
+SessionService::SessionService(const std::wstring& save_path)
+    : BaseSessionService(SESSION_RESTORE, NULL, save_path),
+      has_open_tabbed_browsers_(false),
+      move_on_new_browser_(false) {
+  Init();
+}
+
+SessionService::~SessionService() {
+  Save();
+
+  // Unregister our notifications.
+  NotificationService::current()->RemoveObserver(
+      this, NOTIFY_TAB_PARENTED, NotificationService::AllSources());
+  NotificationService::current()->RemoveObserver(
+      this, NOTIFY_TAB_CLOSED, NotificationService::AllSources());
+  NotificationService::current()->RemoveObserver(
+      this, NOTIFY_NAV_LIST_PRUNED, NotificationService::AllSources());
+  NotificationService::current()->RemoveObserver(
+      this, NOTIFY_NAV_ENTRY_CHANGED, NotificationService::AllSources());
+  NotificationService::current()->RemoveObserver(
+      this, NOTIFY_NAV_ENTRY_COMMITTED, NotificationService::AllSources());
+  NotificationService::current()->RemoveObserver(
+      this, NOTIFY_BROWSER_OPENED, NotificationService::AllSources());
+}
+
+void SessionService::ResetFromCurrentBrowsers() {
+  ScheduleReset();
+}
+
+void SessionService::MoveCurrentSessionToLastSession() {
+  pending_tab_close_ids_.clear();
+  window_closing_ids_.clear();
+  pending_window_close_ids_.clear();
+
+  Save();
+
+  if (!backend_thread()) {
+    backend()->MoveCurrentSessionToLastSession();
+  } else {
+    backend_thread()->message_loop()->PostTask(FROM_HERE, NewRunnableMethod(
+        backend(), &SessionBackend::MoveCurrentSessionToLastSession));
+  }
+}
+
+void SessionService::SetTabWindow(const SessionID& window_id,
+                                  const SessionID& tab_id) {
+  if (!ShouldTrackChangesToWindow(window_id))
+    return;
+
+  ScheduleCommand(CreateSetTabWindowCommand(window_id, tab_id));
+}
+
+void SessionService::SetWindowBounds(const SessionID& window_id,
+                                     const gfx::Rect& bounds,
+                                     bool is_maximized) {
+  if (!ShouldTrackChangesToWindow(window_id))
+    return;
+
+  ScheduleCommand(CreateSetWindowBoundsCommand(window_id, bounds,
+                                               is_maximized));
+}
+
+void SessionService::SetTabIndexInWindow(const SessionID& window_id,
+                                         const SessionID& tab_id,
+                                         int new_index) {
+  if (!ShouldTrackChangesToWindow(window_id))
+    return;
+
+  ScheduleCommand(CreateSetTabIndexInWindowCommand(tab_id, new_index));
+}
+
+void SessionService::TabClosed(const SessionID& window_id,
+                               const SessionID& tab_id) {
+  if (!ShouldTrackChangesToWindow(window_id))
+    return;
+
+  IdToRange::iterator i = tab_to_available_range_.find(tab_id.id());
+  if (i != tab_to_available_range_.end())
+    tab_to_available_range_.erase(i);
+
+  if (find(pending_window_close_ids_.begin(), pending_window_close_ids_.end(),
+           window_id.id()) != pending_window_close_ids_.end()) {
+    // Tab is in last window. Don't commit it immediately, instead add it to the
+    // list of tabs to close. If the user creates another window, the close is
+    // committed.
+    pending_tab_close_ids_.insert(tab_id.id());
+  } else if (find(window_closing_ids_.begin(), window_closing_ids_.end(),
+                  window_id.id()) != window_closing_ids_.end() ||
+             !IsOnlyOneTabLeft()) {
+    // Tab closure is the result of a window close (and it isn't the last
+    // window), or closing a tab and there are other windows/tabs open. Mark the
+    // tab as closed.
+    ScheduleCommand(CreateTabClosedCommand(tab_id.id()));
+  } else {
+    // User closed the last tab in the last tabbed browser. Don't mark the
+    // tab closed.
+    pending_tab_close_ids_.insert(tab_id.id());
+    has_open_tabbed_browsers_ = false;
+  }
+}
+
+void SessionService::WindowClosing(const SessionID& window_id) {
+  if (!ShouldTrackChangesToWindow(window_id))
+    return;
+
+  // The window is about to close. If there are other tabbed browsers with the
+  // same original profile commit the close immediately.
+  //
+  // NOTE: if the user chooses the exit menu item session service is destroyed
+  // and this code isn't hit.
+  if (has_open_tabbed_browsers_) {
+    // Closing a window can never make has_open_tabbed_browsers_ go from false
+    // to true, so only update it if already true.
+    has_open_tabbed_browsers_ = HasOpenTabbedBrowsers(window_id);
+  }
+  if (!has_open_tabbed_browsers_)
+    pending_window_close_ids_.insert(window_id.id());
+  else
+    window_closing_ids_.insert(window_id.id());
+}
+
+void SessionService::WindowClosed(const SessionID& window_id) {
+  if (!ShouldTrackChangesToWindow(window_id))
+    return;
+
+  windows_tracking_.erase(window_id.id());
+
+  if (window_closing_ids_.find(window_id.id()) != window_closing_ids_.end()) {
+    window_closing_ids_.erase(window_id.id());
+    ScheduleCommand(CreateWindowClosedCommand(window_id.id()));
+  } else if (pending_window_close_ids_.find(window_id.id()) ==
+             pending_window_close_ids_.end()) {
+    // We'll hit this if user closed the last tab in a window.
+    has_open_tabbed_browsers_ = HasOpenTabbedBrowsers(window_id);
+    if (!has_open_tabbed_browsers_)
+      pending_window_close_ids_.insert(window_id.id());
+    else
+      ScheduleCommand(CreateWindowClosedCommand(window_id.id()));
+  }
+}
+
+void SessionService::SetWindowType(const SessionID& window_id,
+                                   Browser::Type type) {
+  if (!should_track_changes_for_browser_type(type))
+    return;
+
+  windows_tracking_.insert(window_id.id());
+
+  // The user created a new tabbed browser with our profile. Commit any
+  // pending closes.
+  CommitPendingCloses();
+
+  has_open_tabbed_browsers_ = true;
+  move_on_new_browser_ = true;
+
+  ScheduleCommand(CreateSetWindowTypeCommand(window_id, type));
+}
+
+void SessionService::TabNavigationPathPrunedFromBack(const SessionID& window_id,
+                                                     const SessionID& tab_id,
+                                                     int count) {
+  if (!ShouldTrackChangesToWindow(window_id))
+    return;
+
+  TabNavigationPathPrunedFromBackPayload payload = { 0 };
+  payload.id = tab_id.id();
+  payload.index = count;
+  SessionCommand* command =
+      new SessionCommand(kCommandTabNavigationPathPrunedFromBack,
+                         sizeof(payload));
+  memcpy(command->contents(), &payload, sizeof(payload));
+  ScheduleCommand(command);
+}
+
+void SessionService::TabNavigationPathPrunedFromFront(
+    const SessionID& window_id,
+    const SessionID& tab_id,
+    int count) {
+  if (!ShouldTrackChangesToWindow(window_id))
+    return;
+
+  // Update the range of indices.
+  if (tab_to_available_range_.find(tab_id.id()) !=
+      tab_to_available_range_.end()) {
+    std::pair<int, int>& range = tab_to_available_range_[tab_id.id()];
+    range.first = std::max(0, range.first - count);
+    range.second = std::max(0, range.second - count);
+  }
+
+  TabNavigationPathPrunedFromFrontPayload payload = { 0 };
+  payload.id = tab_id.id();
+  payload.index = count;
+  SessionCommand* command =
+      new SessionCommand(kCommandTabNavigationPathPrunedFromFront,
+                         sizeof(payload));
+  memcpy(command->contents(), &payload, sizeof(payload));
+  ScheduleCommand(command);
+}
+
+void SessionService::UpdateTabNavigation(const SessionID& window_id,
+                                         const SessionID& tab_id,
+                                         int index,
+                                         const NavigationEntry& entry) {
+  if (!ShouldTrackEntry(entry) || !ShouldTrackChangesToWindow(window_id))
+    return;
+
+  if (tab_to_available_range_.find(tab_id.id()) !=
+      tab_to_available_range_.end()) {
+    std::pair<int, int>& range = tab_to_available_range_[tab_id.id()];
+    range.first = std::min(index, range.first);
+    range.second = std::max(index, range.second);
+  }
+  ScheduleCommand(CreateUpdateTabNavigationCommand(kCommandUpdateTabNavigation,
+                                                   tab_id.id(), index, entry));
+}
+
+void SessionService::TabRestored(NavigationController* controller) {
+  if (!ShouldTrackChangesToWindow(controller->window_id()))
+    return;
+
+  BuildCommandsForTab(controller->window_id(), controller, -1,
+                      &pending_commands(), NULL);
+  StartSaveTimer();
+}
+
+void SessionService::SetSelectedNavigationIndex(const SessionID& window_id,
+                                                const SessionID& tab_id,
+                                                int index) {
+  if (!ShouldTrackChangesToWindow(window_id))
+    return;
+
+  if (tab_to_available_range_.find(tab_id.id()) !=
+      tab_to_available_range_.end()) {
+    if (index < tab_to_available_range_[tab_id.id()].first ||
+        index > tab_to_available_range_[tab_id.id()].second) {
+      // The new index is outside the range of what we've archived, schedule
+      // a reset.
+      ResetFromCurrentBrowsers();
+      return;
+    }
+  }
+  ScheduleCommand(CreateSetSelectedNavigationIndexCommand(tab_id, index));
+}
+
+void SessionService::SetSelectedTabInWindow(const SessionID& window_id,
+                                            int index) {
+  if (!ShouldTrackChangesToWindow(window_id))
+    return;
+
+  ScheduleCommand(CreateSetSelectedTabInWindow(window_id, index));
+}
+
+SessionService::Handle SessionService::GetLastSession(
+    CancelableRequestConsumerBase* consumer,
+    LastSessionCallback* callback) {
+  return ScheduleGetLastSessionCommands(
+      new InternalLastSessionRequest(
+          NewCallback(this, &SessionService::OnGotLastSessionCommands),
+          callback), consumer);
+}
+
+void SessionService::Init() {
+  // Register for the notifications we're interested in.
+  NotificationService::current()->AddObserver(
+      this, NOTIFY_TAB_PARENTED, NotificationService::AllSources());
+  NotificationService::current()->AddObserver(
+      this, NOTIFY_TAB_CLOSED, NotificationService::AllSources());
+  NotificationService::current()->AddObserver(
+      this, NOTIFY_NAV_LIST_PRUNED, NotificationService::AllSources());
+  NotificationService::current()->AddObserver(
+      this, NOTIFY_NAV_ENTRY_CHANGED, NotificationService::AllSources());
+  NotificationService::current()->AddObserver(
+      this, NOTIFY_NAV_ENTRY_COMMITTED, NotificationService::AllSources());
+  NotificationService::current()->AddObserver(
+      this, NOTIFY_BROWSER_OPENED, NotificationService::AllSources());
+}
+
+void SessionService::Observe(NotificationType type,
+                             const NotificationSource& source,
+                             const NotificationDetails& details) {
+  // All of our messages have the NavigationController as the source.
+  switch (type) {
+    case NOTIFY_BROWSER_OPENED: {
+      Browser* browser = Source<Browser>(source).ptr();
+      if (browser->profile() != profile() ||
+          !should_track_changes_for_browser_type(browser->type())) {
+        return;
+      }
+
+      if (!has_open_tabbed_browsers_ && !BrowserInit::InProcessStartup()) {
+        // We're going from no tabbed browsers to a tabbed browser (and not in
+        // process startup), restore the last session.
+        if (move_on_new_browser_) {
+          // Make the current session the last.
+          MoveCurrentSessionToLastSession();
+          move_on_new_browser_ = false;
+        }
+        SessionStartupPref pref = SessionStartupPref::GetStartupPref(profile());
+        if (pref.type == SessionStartupPref::LAST) {
+          SessionRestore::RestoreSession(
+              profile(), browser, false, false, std::vector<GURL>());
+        }
+      }
+      SetWindowType(browser->session_id(), browser->type());
+      break;
+    }
+
+    case NOTIFY_TAB_PARENTED: {
+      NavigationController* controller =
+          Source<NavigationController>(source).ptr();
+      SetTabWindow(controller->window_id(), controller->session_id());
+      break;
+    }
+
+    case NOTIFY_TAB_CLOSED: {
+      NavigationController* controller =
+          Source<NavigationController>(source).ptr();
+      TabClosed(controller->window_id(), controller->session_id());
+      break;
+    }
+
+    case NOTIFY_NAV_LIST_PRUNED: {
+      NavigationController* controller =
+          Source<NavigationController>(source).ptr();
+      Details<NavigationController::PrunedDetails> pruned_details(details);
+      if (pruned_details->from_front) {
+        TabNavigationPathPrunedFromFront(controller->window_id(),
+                                         controller->session_id(),
+                                         pruned_details->count);
+      } else {
+        TabNavigationPathPrunedFromBack(controller->window_id(),
+                                        controller->session_id(),
+                                        controller->GetEntryCount());
+      }
+      break;
+    }
+
+    case NOTIFY_NAV_ENTRY_CHANGED: {
+      NavigationController* controller =
+          Source<NavigationController>(source).ptr();
+      Details<NavigationController::EntryChangedDetails> changed(details);
+      UpdateTabNavigation(controller->window_id(), controller->session_id(),
+                          changed->index, *changed->changed_entry);
+      break;
+    }
+
+    case NOTIFY_NAV_ENTRY_COMMITTED: {
+      NavigationController* controller =
+          Source<NavigationController>(source).ptr();
+      int current_entry_index = controller->GetCurrentEntryIndex();
+      SetSelectedNavigationIndex(controller->window_id(),
+                                 controller->session_id(),
+                                 current_entry_index);
+      UpdateTabNavigation(controller->window_id(), controller->session_id(),
+                          current_entry_index,
+                          *controller->GetEntryAtIndex(current_entry_index));
+      break;
+    }
+
+    default:
+      NOTREACHED();
+  }
+}
+
+SessionCommand* SessionService::CreateSetSelectedTabInWindow(
+    const SessionID& window_id,
+    int index) {
+  SelectedTabInIndexPayload payload = { 0 };
+  payload.id = window_id.id();
+  payload.index = index;
+  SessionCommand* command = new SessionCommand(kCommandSetSelectedTabInIndex,
+                                 sizeof(payload));
+  memcpy(command->contents(), &payload, sizeof(payload));
+  return command;
+}
+
+SessionCommand* SessionService::CreateSetTabWindowCommand(
+    const SessionID& window_id,
+    const SessionID& tab_id) {
+  SessionID::id_type payload[] = { window_id.id(), tab_id.id() };
+  SessionCommand* command =
+      new SessionCommand(kCommandSetTabWindow, sizeof(payload));
+  memcpy(command->contents(), payload, sizeof(payload));
+  return command;
+}
+
+SessionCommand* SessionService::CreateSetWindowBoundsCommand(
+    const SessionID& window_id,
+    const gfx::Rect& bounds,
+    bool is_maximized) {
+  WindowBoundsPayload2 payload = { 0 };
+  payload.window_id = window_id.id();
+  payload.x = bounds.x();
+  payload.y = bounds.y();
+  payload.w = bounds.width();
+  payload.h = bounds.height();
+  payload.is_maximized = is_maximized;
+  SessionCommand* command = new SessionCommand(kCommandSetWindowBounds2,
+                                               sizeof(payload));
+  memcpy(command->contents(), &payload, sizeof(payload));
+  return command;
+}
+
+SessionCommand* SessionService::CreateSetTabIndexInWindowCommand(
+    const SessionID& tab_id,
+    int new_index) {
+  TabIndexInWindowPayload payload = { 0 };
+  payload.id = tab_id.id();
+  payload.index = new_index;
+  SessionCommand* command =
+      new SessionCommand(kCommandSetTabIndexInWindow, sizeof(payload));
+  memcpy(command->contents(), &payload, sizeof(payload));
+  return command;
+}
+
+SessionCommand* SessionService::CreateTabClosedCommand(
+    const SessionID::id_type tab_id) {
+  ClosedPayload payload;
+  // Because of what appears to be a compiler bug setting payload to {0} doesn't
+  // set the padding to 0, resulting in Purify reporting an UMR when we write
+  // the structure to disk. To avoid this we explicitly memset the struct.
+  memset(&payload, 0, sizeof(payload));
+  payload.id = tab_id;
+  payload.close_time = Time::Now().ToInternalValue();
+  SessionCommand* command =
+      new SessionCommand(kCommandTabClosed, sizeof(payload));
+  memcpy(command->contents(), &payload, sizeof(payload));
+  return command;
+}
+
+SessionCommand* SessionService::CreateWindowClosedCommand(
+    const SessionID::id_type window_id) {
+  ClosedPayload payload;
+  // See comment in CreateTabClosedCommand as to why we do this.
+  memset(&payload, 0, sizeof(payload));
+  payload.id = window_id;
+  payload.close_time = Time::Now().ToInternalValue();
+  SessionCommand* command =
+      new SessionCommand(kCommandWindowClosed, sizeof(payload));
+  memcpy(command->contents(), &payload, sizeof(payload));
+  return command;
+}
+
+SessionCommand* SessionService::CreateSetSelectedNavigationIndexCommand(
+    const SessionID& tab_id,
+    int index) {
+  SelectedNavigationIndexPayload payload = { 0 };
+  payload.id = tab_id.id();
+  payload.index = index;
+  SessionCommand* command = new SessionCommand(
+      kCommandSetSelectedNavigationIndex, sizeof(payload));
+  memcpy(command->contents(), &payload, sizeof(payload));
+  return command;
+}
+
+SessionCommand* SessionService::CreateSetWindowTypeCommand(
+    const SessionID& window_id,
+    Browser::Type type) {
+      WindowTypePayload payload = { 0 };
+  payload.id = window_id.id();
+  payload.index = static_cast<int32>(type);
+  SessionCommand* command = new SessionCommand(
+      kCommandSetWindowType, sizeof(payload));
+  memcpy(command->contents(), &payload, sizeof(payload));
+  return command;
+}
+
+void SessionService::OnGotLastSessionCommands(
+    Handle handle,
+    scoped_refptr<InternalGetCommandsRequest> request) {
+  if (request->canceled())
+    return;
+  ScopedVector<SessionWindow> valid_windows;
+  RestoreSessionFromCommands(
+      request->commands, &(valid_windows.get()));
+  static_cast<InternalLastSessionRequest*>(request.get())->
+      real_callback->RunWithParams(
+          LastSessionCallback::TupleType(request->handle(),
+                                         &(valid_windows.get())));
+}
+
+void SessionService::RestoreSessionFromCommands(
+    const std::vector<SessionCommand*>& commands,
+    std::vector<SessionWindow*>* valid_windows) {
+  std::map<int, SessionTab*> tabs;
+  std::map<int, SessionWindow*> windows;
+
+  if (CreateTabsAndWindows(commands, &tabs, &windows)) {
+    AddTabsToWindows(&tabs, &windows);
+    SortTabsBasedOnVisualOrderAndPrune(&windows, valid_windows);
+    UpdateSelectedTabIndex(valid_windows);
+  }
+  STLDeleteValues(&tabs);
+  // Don't delete conents of windows, that is done by the caller as all
+  // valid windows are added to valid_windows.
+}
+
+void SessionService::UpdateSelectedTabIndex(
+    std::vector<SessionWindow*>* windows) {
+  for (std::vector<SessionWindow*>::const_iterator i = windows->begin();
+       i != windows->end(); ++i) {
+    // See note in SessionWindow as to why we do this.
+    int new_index = 0;
+    for (std::vector<SessionTab*>::const_iterator j = (*i)->tabs.begin();
+         j != (*i)->tabs.end(); ++j) {
+      if ((*j)->tab_visual_index == (*i)->selected_tab_index) {
+        new_index = static_cast<int>(j - (*i)->tabs.begin());
+        break;
+      }
+    }
+    (*i)->selected_tab_index = new_index;
+  }
+}
+
+SessionWindow* SessionService::GetWindow(
+    SessionID::id_type window_id,
+    IdToSessionWindow* windows) {
+  std::map<int, SessionWindow*>::iterator i = windows->find(window_id);
+  if (i == windows->end()) {
+    SessionWindow* window = new SessionWindow();
+    window->window_id.set_id(window_id);
+    (*windows)[window_id] = window;
+    return window;
+  }
+  return i->second;
+}
+
+SessionTab* SessionService::GetTab(
+    SessionID::id_type tab_id,
+    IdToSessionTab* tabs) {
+  DCHECK(tabs);
+  std::map<int, SessionTab*>::iterator i = tabs->find(tab_id);
+  if (i == tabs->end()) {
+    SessionTab* tab = new SessionTab();
+    tab->tab_id.set_id(tab_id);
+    (*tabs)[tab_id] = tab;
+    return tab;
+  }
+  return i->second;
+}
+
+std::vector<TabNavigation>::iterator
+  SessionService::FindClosestNavigationWithIndex(
+    std::vector<TabNavigation>* navigations,
+    int index) {
+  DCHECK(navigations);
+  for (std::vector<TabNavigation>::iterator i = navigations->begin();
+       i != navigations->end(); ++i) {
+    if (i->index() >= index)
+      return i;
+  }
+  return navigations->end();
+}
+
+// Function used in sorting windows. Sorting is done based on window id. As
+// window ids increment for each new window, this effectively sorts by creation
+// time.
+static bool WindowOrderSortFunction(const SessionWindow* w1,
+                                    const SessionWindow* w2) {
+  return w1->window_id.id() < w2->window_id.id();
+}
+
+// Compares the two tabs based on visual index.
+static bool TabVisualIndexSortFunction(const SessionTab* t1,
+                                       const SessionTab* t2) {
+  const int delta = t1->tab_visual_index - t2->tab_visual_index;
+  return delta == 0 ? (t1->tab_id.id() < t2->tab_id.id()) : (delta < 0);
+}
+
+void SessionService::SortTabsBasedOnVisualOrderAndPrune(
+    std::map<int, SessionWindow*>* windows,
+    std::vector<SessionWindow*>* valid_windows) {
+  std::map<int, SessionWindow*>::iterator i = windows->begin();
+  while (i != windows->end()) {
+    if (i->second->tabs.empty() || i->second->is_constrained ||
+        !should_track_changes_for_browser_type(i->second->type)) {
+      delete i->second;
+      i = windows->erase(i);
+    } else {
+      // Valid window; sort the tabs and add it to the list of valid windows.
+      std::sort(i->second->tabs.begin(), i->second->tabs.end(),
+                &TabVisualIndexSortFunction);
+      // Add the window such that older windows appear first.
+      if (valid_windows->empty()) {
+        valid_windows->push_back(i->second);
+      } else {
+        valid_windows->insert(
+            std::upper_bound(valid_windows->begin(), valid_windows->end(),
+                             i->second, &WindowOrderSortFunction),
+            i->second);
+      }
+      ++i;
+    }
+  }
+}
+
+void SessionService::AddTabsToWindows(std::map<int, SessionTab*>* tabs,
+                                      std::map<int, SessionWindow*>* windows) {
+  std::map<int, SessionTab*>::iterator i = tabs->begin();
+  while (i != tabs->end()) {
+    SessionTab* tab = i->second;
+    if (tab->window_id.id() && !tab->navigations.empty()) {
+      SessionWindow* window = GetWindow(tab->window_id.id(), windows);
+      window->tabs.push_back(tab);
+      i = tabs->erase(i);
+
+      // See note in SessionTab as to why we do this.
+      std::vector<TabNavigation>::iterator j =
+          FindClosestNavigationWithIndex(&(tab->navigations),
+                                         tab->current_navigation_index);
+      if (j == tab->navigations.end()) {
+        tab->current_navigation_index =
+            static_cast<int>(tab->navigations.size() - 1);
+      } else {
+        tab->current_navigation_index =
+            static_cast<int>(j - tab->navigations.begin());
+      }
+    } else {
+      // Never got a set tab index in window, or tabs are empty, nothing
+      // to do.
+      ++i;
+    }
+  }
+}
+
+bool SessionService::CreateTabsAndWindows(
+    const std::vector<SessionCommand*>& data,
+    std::map<int, SessionTab*>* tabs,
+    std::map<int, SessionWindow*>* windows) {
+  // If the file is corrupt (command with wrong size, or unknown command), we
+  // still return true and attempt to restore what we we can.
+
+  for (std::vector<SessionCommand*>::const_iterator i = data.begin();
+       i != data.end(); ++i) {
+    const SessionCommand* command = *i;
+
+    switch (command->id()) {
+      case kCommandSetTabWindow: {
+        SessionID::id_type payload[2];
+        if (!command->GetPayload(payload, sizeof(payload)))
+          return true;
+        GetTab(payload[1], tabs)->window_id.set_id(payload[0]);
+        break;
+      }
+
+      case kCommandSetWindowBounds2: {
+        WindowBoundsPayload2 payload;
+        if (!command->GetPayload(&payload, sizeof(payload)))
+          return true;
+        GetWindow(payload.window_id, windows)->bounds.SetRect(payload.x,
+                                                              payload.y,
+                                                              payload.w,
+                                                              payload.h);
+        GetWindow(payload.window_id, windows)->is_maximized =
+            payload.is_maximized;
+        break;
+      }
+
+      case kCommandSetTabIndexInWindow: {
+        TabIndexInWindowPayload payload;
+        if (!command->GetPayload(&payload, sizeof(payload)))
+          return true;
+        GetTab(payload.id, tabs)->tab_visual_index = payload.index;
+        break;
+      }
+
+      case kCommandTabClosed:
+      case kCommandWindowClosed: {
+        ClosedPayload payload;
+        if (!command->GetPayload(&payload, sizeof(payload)))
+          return true;
+        if (command->id() == kCommandTabClosed) {
+          delete GetTab(payload.id, tabs);
+          tabs->erase(payload.id);
+        } else {
+          delete GetWindow(payload.id, windows);
+          windows->erase(payload.id);
+        }
+        break;
+      }
+
+      case kCommandTabNavigationPathPrunedFromBack: {
+        TabNavigationPathPrunedFromBackPayload payload;
+        if (!command->GetPayload(&payload, sizeof(payload)))
+          return true;
+        SessionTab* tab = GetTab(payload.id, tabs);
+        tab->navigations.erase(
+            FindClosestNavigationWithIndex(&(tab->navigations), payload.index),
+            tab->navigations.end());
+        break;
+      }
+
+      case kCommandTabNavigationPathPrunedFromFront: {
+        TabNavigationPathPrunedFromFrontPayload payload;
+        if (!command->GetPayload(&payload, sizeof(payload)) ||
+            payload.index <= 0) {
+          return true;
+        }
+        SessionTab* tab = GetTab(payload.id, tabs);
+
+        // Update the selected navigation index.
+        tab->current_navigation_index =
+            std::max(-1, tab->current_navigation_index - payload.index);
+        
+        // And update the index of existing navigations.
+        for (std::vector<TabNavigation>::iterator i = tab->navigations.begin();
+             i != tab->navigations.end();) {
+          i->set_index(i->index() - payload.index);
+          if (i->index() < 0)
+            i = tab->navigations.erase(i);
+          else
+            ++i;
+        }
+        break;
+      }
+
+      case kCommandUpdateTabNavigation: {
+        TabNavigation navigation;
+        SessionID::id_type tab_id;
+        if (!RestoreUpdateTabNavigationCommand(*command, &navigation, &tab_id))
+          return true;
+
+        SessionTab* tab = GetTab(tab_id, tabs);
+        std::vector<TabNavigation>::iterator i =
+            FindClosestNavigationWithIndex(&(tab->navigations),
+                                           navigation.index());
+        if (i != tab->navigations.end() && i->index() == navigation.index())
+          *i = navigation;
+        else
+          tab->navigations.insert(i, navigation);
+        break;
+      }
+
+      case kCommandSetSelectedNavigationIndex: {
+        SelectedNavigationIndexPayload payload;
+        if (!command->GetPayload(&payload, sizeof(payload)))
+          return true;
+        GetTab(payload.id, tabs)->current_navigation_index = payload.index;
+        break;
+      }
+
+      case kCommandSetSelectedTabInIndex: {
+        SelectedTabInIndexPayload payload;
+        if (!command->GetPayload(&payload, sizeof(payload)))
+          return true;
+        GetWindow(payload.id, windows)->selected_tab_index = payload.index;
+        break;
+      }
+
+      case kCommandSetWindowType: {
+        WindowTypePayload payload;
+        if (!command->GetPayload(&payload, sizeof(payload)))
+          return true;
+        GetWindow(payload.id, windows)->is_constrained = false;
+        GetWindow(payload.id, windows)->type =
+            static_cast<Browser::Type>(payload.index);
+        break;
+      }
+
+      default:
+        return true;
+    }
+  }
+  return true;
+}
+
+void SessionService::BuildCommandsForTab(
+    const SessionID& window_id,
+    NavigationController* controller,
+    int index_in_window,
+    std::vector<SessionCommand*>* commands,
+    IdToRange* tab_to_available_range) {
+  DCHECK(controller && commands && window_id.id());
+  commands->push_back(
+      CreateSetTabWindowCommand(window_id, controller->session_id()));
+  const int current_index = controller->GetCurrentEntryIndex();
+  const int min_index = std::max(0,
+                                 current_index - max_persist_navigation_count);
+  const int max_index = std::min(current_index + max_persist_navigation_count,
+                                 controller->GetEntryCount());
+  const int pending_index = controller->GetPendingEntryIndex();
+  if (tab_to_available_range) {
+    (*tab_to_available_range)[controller->session_id().id()] =
+        std::pair<int, int>(min_index, max_index);
+  }
+  for (int i = min_index; i < max_index; ++i) {
+    const NavigationEntry* entry = (i == pending_index) ?
+        controller->GetPendingEntry() : controller->GetEntryAtIndex(i);
+    DCHECK(entry);
+    if (ShouldTrackEntry(*entry)) {
+      commands->push_back(
+          CreateUpdateTabNavigationCommand(kCommandUpdateTabNavigation,
+                                           controller->session_id().id(),
+                                           i,
+                                           *entry));
+    }
+  }
+  commands->push_back(
+      CreateSetSelectedNavigationIndexCommand(controller->session_id(),
+                                              current_index));
+
+  if (index_in_window != -1) {
+    commands->push_back(
+        CreateSetTabIndexInWindowCommand(controller->session_id(),
+                                         index_in_window));
+  }
+}
+
+void SessionService::BuildCommandsForBrowser(
+    Browser* browser,
+    std::vector<SessionCommand*>* commands,
+    IdToRange* tab_to_available_range,
+    std::set<SessionID::id_type>* windows_to_track) {
+  DCHECK(browser && commands);
+  DCHECK(browser->session_id().id());
+
+  commands->push_back(
+      CreateSetWindowBoundsCommand(browser->session_id(),
+                                   browser->window()->GetNormalBounds(),
+                                   browser->window()->IsMaximized()));
+
+  commands->push_back(CreateSetWindowTypeCommand(
+      browser->session_id(), browser->type()));
+
+  bool added_to_windows_to_track = false;
+  for (int i = 0; i < browser->tab_count(); ++i) {
+    TabContents* tab = browser->GetTabContentsAt(i);
+    DCHECK(tab);
+    if (tab->profile() == profile()) {
+      BuildCommandsForTab(browser->session_id(), tab->controller(), i,
+                          commands, tab_to_available_range);
+      if (windows_to_track && !added_to_windows_to_track) {
+        windows_to_track->insert(browser->session_id().id());
+        added_to_windows_to_track = true;
+      }
+    }
+  }
+  commands->push_back(
+      CreateSetSelectedTabInWindow(browser->session_id(),
+                                   browser->selected_index()));
+}
+
+void SessionService::BuildCommandsFromBrowsers(
+    std::vector<SessionCommand*>* commands,
+    IdToRange* tab_to_available_range,
+    std::set<SessionID::id_type>* windows_to_track) {
+  DCHECK(commands);
+  for (BrowserList::const_iterator i = BrowserList::begin();
+       i != BrowserList::end(); ++i) {
+    // Make sure the browser has tabs and a window. Browsers destructor
+    // removes itself from the BrowserList. When a browser is closed the
+    // destructor is not necessarily run immediately. This means its possible
+    // for us to get a handle to a browser that is about to be removed. If
+    // the tab count is 0 or the window is NULL, the browser is about to be
+    // deleted, so we ignore it.
+    if (should_track_changes_for_browser_type((*i)->type()) &&
+        (*i)->tab_count() && (*i)->window()) {
+      BuildCommandsForBrowser(*i, commands, tab_to_available_range,
+                              windows_to_track);
+    }
+  }
+}
+
+void SessionService::ScheduleReset() {
+  set_pending_reset(true);
+  STLDeleteElements(&pending_commands());
+  tab_to_available_range_.clear();
+  windows_tracking_.clear();
+  BuildCommandsFromBrowsers(&pending_commands(), &tab_to_available_range_,
+                            &windows_tracking_);
+  if (!windows_tracking_.empty()) {
+    // We're lazily created on startup and won't get an initial batch of
+    // SetWindowType messages. Set these here to make sure our state is correct.
+    has_open_tabbed_browsers_ = true;
+    move_on_new_browser_ = true;
+  }
+  StartSaveTimer();
+}
+
+bool SessionService::ReplacePendingCommand(SessionCommand* command) {
+  // We only optimize page navigations, which can happen quite frequently and
+  // are expensive. If necessary, other commands could be searched for as
+  // well.
+  if (command->id() != kCommandUpdateTabNavigation)
+    return false;
+  void* iterator = NULL;
+  scoped_ptr<Pickle> command_pickle(command->PayloadAsPickle());
+  SessionID::id_type command_tab_id;
+  int command_nav_index;
+  if (!command_pickle->ReadInt(&iterator, &command_tab_id) ||
+      !command_pickle->ReadInt(&iterator, &command_nav_index)) {
+    return false;
+  }
+  for (std::vector<SessionCommand*>::reverse_iterator i =
+       pending_commands().rbegin(); i != pending_commands().rend(); ++i) {
+    SessionCommand* existing_command = *i;
+    if (existing_command->id() == kCommandUpdateTabNavigation) {
+      SessionID::id_type existing_tab_id;
+      int existing_nav_index;
+      scoped_ptr<Pickle> existing_pickle(existing_command->PayloadAsPickle());
+      iterator = NULL;
+      if (!existing_pickle->ReadInt(&iterator, &existing_tab_id) ||
+          !existing_pickle->ReadInt(&iterator, &existing_nav_index)) {
+        return false;
+      }
+      if (existing_tab_id == command_tab_id &&
+          existing_nav_index == command_nav_index) {
+        // existing_command is an update for the same tab/index pair. Replace
+        // it with the new one. We need to add to the end of the list just in
+        // case there is a prune command after the update command.
+        delete existing_command;
+        pending_commands().erase(i.base() - 1);
+        pending_commands().push_back(command);
+        return true;
+      }
+      return false;
+    }
+  }
+  return false;
+}
+
+void SessionService::ScheduleCommand(SessionCommand* command) {
+  DCHECK(command);
+  if (ReplacePendingCommand(command))
+    return;
+  BaseSessionService::ScheduleCommand(command);
+  // Don't schedule a reset on tab closed/window closed. Otherwise we may
+  // lose tabs/windows we want to restore from if we exit right after this.
+  if (!pending_reset() && pending_window_close_ids_.empty() &&
+      commands_since_reset() >= kWritesPerReset &&
+      (command->id() != kCommandTabClosed &&
+       command->id() != kCommandWindowClosed)) {
+    ScheduleReset();
+  }
+}
+
+void SessionService::CommitPendingCloses() {
+  for (PendingTabCloseIDs::iterator i = pending_tab_close_ids_.begin();
+       i != pending_tab_close_ids_.end(); ++i) {
+    ScheduleCommand(CreateTabClosedCommand(*i));
+  }
+  pending_tab_close_ids_.clear();
+
+  for (PendingWindowCloseIDs::iterator i = pending_window_close_ids_.begin();
+       i != pending_window_close_ids_.end(); ++i) {
+    ScheduleCommand(CreateWindowClosedCommand(*i));
+  }
+  pending_window_close_ids_.clear();
+}
+
+bool SessionService::IsOnlyOneTabLeft() {
+  if (!profile()) {
+    // We're testing, always return false.
+    return false;
+  }
+
+  // NOTE: This uses the original profile so that closing the last non-off the
+  // record window while there are open off the record window resets state).
+  int window_count = 0;
+  for (BrowserList::const_iterator i = BrowserList::begin();
+       i != BrowserList::end(); ++i) {
+    const SessionID::id_type window_id = (*i)->session_id().id();
+    if (should_track_changes_for_browser_type((*i)->type()) &&
+        (*i)->profile()->GetOriginalProfile() == profile() &&
+        window_closing_ids_.find(window_id) == window_closing_ids_.end()) {
+      if (++window_count > 1)
+        return false;
+      // By the time this is invoked the tab has been removed. As such, we use
+      // > 0 here rather than > 1.
+      if ((*i)->tab_count() > 0)
+        return false;
+    }
+  }
+  return true;
+}
+
+bool SessionService::HasOpenTabbedBrowsers(const SessionID& window_id) {
+  if (!profile()) {
+    // We're testing, always return false.
+    return true;
+  }
+
+  // NOTE: This uses the original profile so that closing the last non-off the
+  // record window while there are open off the record window resets state).
+  for (BrowserList::const_iterator i = BrowserList::begin();
+       i != BrowserList::end(); ++i) {
+    Browser* browser = *i;
+    const SessionID::id_type browser_id = browser->session_id().id();
+    if (browser_id != window_id.id() &&
+        window_closing_ids_.find(browser_id) == window_closing_ids_.end() &&
+        should_track_changes_for_browser_type(browser->type()) &&
+        browser->profile()->GetOriginalProfile() == profile()) {
+      return true;
+    }
+  }
+  return false;
+}
+
+bool SessionService::ShouldTrackChangesToWindow(const SessionID& window_id) {
+  return windows_tracking_.find(window_id.id()) != windows_tracking_.end();
+}