[SYNC] Sessions datatype refactor. Most things related to sessions under-the-...

chrome/browser/sync/glue/session_model_associator.h

Index: chrome/browser/sync/glue/session_model_associator.h
===================================================================
--- chrome/browser/sync/glue/session_model_associator.h	(revision 69693)
+++ chrome/browser/sync/glue/session_model_associator.h	(working copy)
@@ -6,6 +6,8 @@
 #define CHROME_BROWSER_SYNC_GLUE_SESSION_MODEL_ASSOCIATOR_H_
 #pragma once
 
+#include <map>
+#include <set>
 #include <string>
 #include <vector>
 
@@ -13,12 +15,17 @@
 #include "base/gtest_prod_util.h"
 #include "base/observer_list.h"
 #include "base/scoped_vector.h"
+#include "base/string_util.h"
+#include "base/utf_string_conversions.h"
+#include "chrome/browser/browser_window.h"
+#include "chrome/browser/sessions/session_id.h"
 #include "chrome/browser/sessions/session_service.h"
 #include "chrome/browser/sessions/session_types.h"
 #include "chrome/browser/sync/engine/syncapi.h"
 #include "chrome/browser/sync/glue/model_associator.h"
 #include "chrome/browser/sync/protocol/session_specifics.pb.h"
 #include "chrome/browser/sync/syncable/model_type.h"
+#include "chrome/browser/tab_contents/tab_contents.h"
 #include "chrome/common/notification_registrar.h"
 
 class Profile;
@@ -38,170 +45,448 @@
 
 static const char kSessionsTag[] = "google_chrome_sessions";
 
+// Class to manage foreign sessions.
+class ForeignSessionTracker {

[tim (not reviewing), 2011/01/04 14:32:47]

this should be in a foreign_session_tracker.h/cc file

[Nicolas Zea, 2011/01/06 01:14:13]

Done.

+ public:
+  ForeignSessionTracker();
+  ~ForeignSessionTracker();
+
+  // Fill a preallocated vector with all foreign sessions we're tracking.
+  // Returns true if we had foreign sessions to fill it with, false otherwise.
+  bool LookupAllForeignSessions(std::vector<const ForeignSession*>* sessions);
+
+  // Attempts to look up the session windows associatd with the foreign session
+  // given by |foreign_session_tag|.
+  // If lookup succeeds:
+  // - Fills windows with the SessionWindow pointers, returns true.
+  // Else
+  // - Returns false.
+  bool LookupSessionWindows(const std::string& foreign_session_tag,
+                            std::vector<SessionWindow*>* windows);
+
+  // Attempts to look up the foreign tab associated with the given tag and tab
+  // id.
+  // If lookup succeeds:
+  // - Sets tab to point to the SessionTab, and returns true.
+  // Else
+  // - Returns false, tab is set to NULL.
+  bool LookupSessionTab(const std::string& foreign_session_tag,
+                        SessionID::id_type tab_id,
+                        const SessionTab** tab);
+
+  // Returns a pointer to the ForeignSession object associated with
+  // foreign_session_tag. If none exists, creates one and returns its pointer.
+  ForeignSession* GetForeignSession(const std::string& foreign_session_tag);
+
+  // Deletes the foreign session associated with |foreign_session_tag| if it
+  // exists.
+  // Returns true if the session existed and was deleted, false otherwise.
+  bool DeleteForeignSession(const std::string& foreign_session_tag);
+
+  // Returns a pointer to the SessionTab object associated with |tab_id| for
+  // the session specified with |foreign_session_tag|. If none exists, creates
+  // one and returns its pointer.
+  // |has_window| determines if newly created tabs are added to the pool of
+  // orphaned tabs (thos which can't be reached by traversing foreign sessions).
+  SessionTab* GetSessionTab(const std::string& foreign_session_tag,
+                            SessionID::id_type tab_id,
+                            bool has_window);
+
+  // Free the memory for all dynamically allocated objects and clear the
+  // tracking structures.
+  void clear();
+
+  inline bool empty() {
+    return foreign_tab_map_.empty() && foreign_session_map_.empty();
+  }
+
+  inline size_t num_foreign_sessions() {
+    return foreign_session_map_.size();
+  }
+
+  inline size_t num_foreign_tabs(const std::string& foreign_session_tag) {
+    if (foreign_tab_map_.find(foreign_session_tag) != foreign_tab_map_.end()) {
+      return foreign_tab_map_[foreign_session_tag]->size();
+    } else {
+      return 0;
+    }
+  }
+ private:

[tim (not reviewing), 2011/01/04 14:32:47]

does the Tracker own all the values in these maps?

[Nicolas Zea, 2011/01/06 01:14:13]

Done.

+  // Datatypes for accessing foreign tab data.
+  typedef std::map<SessionID::id_type, SessionTab*> IDToSessionTabMap;
+  typedef std::map<std::string, IDToSessionTabMap*> ForeignTabMap;
+  typedef std::map<std::string, ForeignSession*> ForeignSessionMap;
+
+  // Per foreign client mapping of their tab id's to their SessionTab objects.
+  ForeignTabMap foreign_tab_map_;
+
+  // Map of foreign sessions, accessed by the foreign client id.
+  ForeignSessionMap foreign_session_map_;
+
+  // The set of foreign tabs that we have seen, and created SessionTab objects
+  // for, but have not yet mapped to ForeignSessions. These are temporarily
+  // orphaned tabs, and won't be deleted if we delete foreign_session_map_.
+  std::set<SessionTab*> unmapped_tabs_;
+
+  DISALLOW_COPY_AND_ASSIGN(ForeignSessionTracker);
+};
+
 // Contains all logic for associating the Chrome sessions model and
 // the sync sessions model.
-// In the case of sessions, our local model is nothing but a buffer (specifics_)
-// that gets overwritten everytime there is an update. From it, we build a new
-// foreign session windows list each time |GetSessionData| is called by the
-// ForeignSessionHandler.
-class SessionModelAssociator : public PerDataTypeAssociatorInterface<
-    sync_pb::SessionSpecifics, std::string>, public NonThreadSafe {
+class SessionModelAssociator
+    : public PerDataTypeAssociatorInterface<TabContents, size_t>,
+      public NonThreadSafe {
  public:
-
   // Does not take ownership of sync_service.
   explicit SessionModelAssociator(ProfileSyncService* sync_service);
   virtual ~SessionModelAssociator();
 
+  // The has_nodes out parameter is set to true if the sync model has
+  // nodes other than the permanent tagged nodes.  The method may
+  // return false if an error occurred.
+  virtual bool SyncModelHasUserCreatedNodes(bool* has_nodes);
+
   // AssociatorInterface and PerDataTypeAssociator Interface implementation.
   virtual void AbortAssociation() {
-    // No implementation needed, this associator runs on the main
-    // thread.
+    // No implementation needed, this associator runs on the main thread.
   }
 
-  // Dummy method, we do everything all-at-once in UpdateFromSyncModel.
-  virtual void Associate(const sync_pb::SessionSpecifics* specifics,
-    int64 sync_id) {
-  }
+  // Returns sync id for the given chrome model id.
+  // Returns sync_api::kInvalidId if the sync node is not found for the given
+  // chrome id.
+  virtual int64 GetSyncIdFromChromeId(const size_t& id);
 
-  // Updates the sync model with the local client data. (calls
-  // UpdateFromSyncModel)
-  virtual bool AssociateModels();
+  // Returns sync id for the given session tag.
+  // Returns sync_api::kInvalidId if the sync node is not found for the given
+  // tag
+  virtual int64 GetSyncIdFromSessionTag(const std::string& tag);
 
-  // The has_nodes out parameter is set to true if the chrome model
-  // has user-created nodes.  The method may return false if an error
-  // occurred.
-  virtual bool ChromeModelHasUserCreatedNodes(bool* has_nodes);
+  // Not used.
+  virtual const TabContents* GetChromeNodeFromSyncId(int64 sync_id) {
+    NOTREACHED();
+    return NULL;
+  }
 
-  // Dummy method, we do everything all-at-once in UpdateFromSyncModel.
-  virtual void Disassociate(int64 sync_id) {
+  // Not used.
+  bool InitSyncNodeFromChromeId(const size_t& id,
+                                sync_api::BaseNode* sync_node) {
+    NOTREACHED();
+    return false;
   }
 
-  // Clear specifics_ buffer and notify foreign session handlers.
-  virtual bool DisassociateModels();
+  // Resync local window information. Updates the local sessions header node
+  // with the status of open windows and the order of tabs they contain. Should
+  // only be called for changes that affect a window, not a change within a
+  // single tab.
+  //
+  // If |reload_tabs| is true, will also resync all tabs (same as calling
+  // ReassociateTabs with a vector of all tabs).
+  void ReassociateWindows(bool reload_tabs);
 
-  // Returns the chrome session specifics for the given sync id.
-  // Returns NULL if no specifics are found for the given sync id.
-  virtual const sync_pb::SessionSpecifics* GetChromeNodeFromSyncId(
-    int64 sync_id);
+  // Loads and reassociates the local tabs referenced in |tabs|.
+  void ReassociateTabs(const std::vector<TabContents*>& tabs);
 
-  // Returns whether a node with the given permanent tag was found and update
-  // |sync_id| with that node's id.
-  virtual bool GetSyncIdForTaggedNode(const std::string* tag, int64* sync_id);
+  // Reassociates a single tab with the sync model. Will check if the tab
+  // already is associated with a sync node and allocate one if necessary.
+  void ReassociateTab(const TabContents& tab);
 
-  // Returns sync id for the given chrome model id.
-  // Returns sync_api::kInvalidId if the sync node is not found for the given
-  // chrome id.
-  virtual int64 GetSyncIdFromChromeId(const std::string& id);
+  // Associate a local tab and it's sync node. Will overwrite the contents of
+  // the sync node with new specifics built from the tab.
+  virtual void Associate(const TabContents* tab, int64 sync_id);
 
+  // Looks up the specified sync node, and marks that tab as closed, then marks
+  // the node as free and deletes association.
+  virtual void Disassociate(int64 sync_id);
 
+  // Load any ƒoreign session info stored in sync db and update the sync db

[tim (not reviewing), 2011/01/04 14:32:47]

whoa, fancy f!

[Nicolas Zea, 2011/01/06 01:14:13]

Done.

+  // with local client data. Processes/reuses any sync nodes owned by this
+  // client and creates any further sync nodes needed to store local header and
+  // tab info.
+  virtual bool AssociateModels();
+
   // Initializes the given sync node from the given chrome node id.
   // Returns false if no sync node was found for the given chrome node id or
   // if the initialization of sync node fails.
   virtual bool InitSyncNodeFromChromeId(const std::string& id,
                                         sync_api::BaseNode* sync_node);
 
-  // The has_nodes out parameter is set to true if the sync model has
-  // nodes other than the permanent tagged nodes.  The method may
-  // return false if an error occurred.
-  virtual bool SyncModelHasUserCreatedNodes(bool* has_nodes);
+  // Clear local sync data buffers. Does not delete sync nodes to avoid
+  // tombstones. TODO(zea): way to eventually delete orphaned nodes.
+  virtual bool DisassociateModels();
 
   // Returns the tag used to uniquely identify this machine's session in the
   // sync model.
-  std::string GetCurrentMachineTag();
+  inline const std::string& GetCurrentMachineTag() {
+    DCHECK(!current_machine_tag_.empty());
+    return current_machine_tag_;
+  }
 
-  // Updates the server data based upon the current client session.  If no node
-  // corresponding to this machine exists in the sync model, one is created.
-  void UpdateSyncModelDataFromClient();
+  // Load and associate window and tab data for a foreign session
+  bool AssociateForeignSpecifics(const sync_pb::SessionSpecifics& specifics,
+                                 int64 modification_time);
 
-  // Pulls the current sync model from the sync database and returns true upon
-  // update of the client model. Called by SessionChangeProcessor.
-  // Note that the specifics_ vector is reset and built from scratch each time.
-  bool UpdateFromSyncModel(const sync_api::BaseTransaction* trans);
+  // Removes a foreign session from our internal bookkeeping.
+  void DisassociateForeignSession(const std::string& foreign_session_tag);
 
-  // Helper for UpdateFromSyncModel. Appends sync data to a vector of specifics.
-  bool QuerySyncModel(const sync_api::BaseTransaction* trans,
-      std::vector<const sync_pb::SessionSpecifics*>& specifics);
+  // Builds a list of all foreign sessions.
+  // Caller does NOT own ForeignSession objects.
+  bool GetAllForeignSessions(std::vector<const ForeignSession*>* sessions);
 
-  // Builds sessions from buffered specifics data
-  bool GetSessionData(std::vector<ForeignSession*>* sessions);
+  // Loads all windows for foreign session with session tag |tag|.
+  // Caller does NOT own ForeignSession objects.
+  bool GetForeignSession(const std::string& tag,
+                         std::vector<SessionWindow*>* windows);
 
-  // Helper method to generate session specifics from session windows.
-  void FillSpecificsFromSessions(std::vector<SessionWindow*>* windows,
-      sync_pb::SessionSpecifics* session);
+  // Looks up the foreign tab identified by |tab_id| and belonging to foreign
+  // session |tag|.
+  // Caller does NOT own the SessionTab object.
+  bool GetForeignTab(const std::string& tag,
+                     const SessionID::id_type tab_id,
+                     const SessionTab** tab);
 
-  // Helper method for converting session specifics to windows.
-  void AppendForeignSessionFromSpecifics(
-      const sync_pb::SessionSpecifics* specifics,
-      std::vector<ForeignSession*>* session);
+  // Specifies whether the window has tabs to sync. The new tab page does not
+  // count. If no tabs to sync, it returns true, otherwise false;
+  static bool SessionWindowHasNoTabsToSync(const SessionWindow& window);
 
-  // Fills the given empty vector with foreign session windows to restore.
-  // If the vector is returned empty, then the session data could not be
-  // converted back into windows.
-  void AppendForeignSessionWithID(int64 id,
-      std::vector<ForeignSession*>* session,
-      sync_api::BaseTransaction* trans);
+  // Control which local tabs we're interested in syncing.
+  // Ensures the profile matches sync's profile and that the tab has at least
+  // one navigation entry and is not an empty tab.
+  bool IsValidTab(const TabContents& tab);
 
+  // Control which foreign tabs we're interested in displaying.
+  // Checks that the tab has navigations and is not a new tab.
+  // Note: a new tab page with back/forward history is valid.
+  static bool IsValidSessionTab(const SessionTab& tab);
+
   // Returns the syncable model type.
   static syncable::ModelType model_type() { return syncable::SESSIONS; }
 
  private:
   FRIEND_TEST_ALL_PREFIXES(ProfileSyncServiceSessionTest, WriteSessionToNode);
   FRIEND_TEST_ALL_PREFIXES(ProfileSyncServiceSessionTest,
+                           WriteFilledSessionToNode);
+  FRIEND_TEST_ALL_PREFIXES(ProfileSyncServiceSessionTest,
                            WriteForeignSessionToNode);
+  FRIEND_TEST_ALL_PREFIXES(ProfileSyncServiceSessionTest, TabNodePoolEmpty);
+  FRIEND_TEST_ALL_PREFIXES(ProfileSyncServiceSessionTest, TabNodePoolNonEmpty);
+  FRIEND_TEST_ALL_PREFIXES(SessionModelAssociatorTest, PopulateSessionWindow);
+  FRIEND_TEST_ALL_PREFIXES(SessionModelAssociatorTest, PopulateSessionTab);
 
-  // Returns the session service from |sync_service_|.
-  SessionService* GetSessionService();
+  // Keep all the links to local tab data in one place.
+  class TabLinks {
+   public:
+    // To support usage as second value in maps we need default and copy
+    // constructors.
+    TabLinks()
+        : sync_id_(0),
+          session_tab_(NULL),
+          tab_(NULL) {}
 
+    // We only ever have either a SessionTab (for foreign tabs), or a
+    // TabContents (for local tabs).
+    TabLinks(int64 sync_id, const TabContents* tab)
+      : sync_id_(sync_id),
+        session_tab_(NULL) {
+      tab_ = const_cast<TabContents*>(tab);
+    }
+    TabLinks(int64 sync_id, const SessionTab* session_tab)
+      : sync_id_(sync_id),
+        tab_(NULL) {
+      session_tab_ = const_cast<SessionTab*>(session_tab);
+    }
+
+    // Getters.

[tim (not reviewing), 2011/01/04 14:32:47]

don't really need this comment.

[Nicolas Zea, 2011/01/06 01:14:13]

Done.

+    inline const int64 sync_id() const { return sync_id_; }
+    inline const SessionTab* session_tab() const { return session_tab_; }
+    inline const TabContents* tab() const { return tab_; }
+   private:
+    int64 sync_id_;
+    SessionTab* session_tab_;
+    TabContents* tab_;
+  };
+
+  // A pool for managing free/used tab sync nodes. Performs lazy creation
+  // of sync nodes when necessary.
+  class TabNodePool {
+  public:

[tim (not reviewing), 2011/01/04 14:32:47]

nit - indent

Did you consider putting TabNodePool in its own file? Fine for now though.

[Nicolas Zea, 2011/01/06 01:14:13]

I did, but since it seemed very session model associator specific, I figured it
was more appropriate in here.

On 2011/01/04 14:32:47, timsteele wrote:

+    explicit TabNodePool(ProfileSyncService* sync_service);
+    TabNodePool(ProfileSyncService* sync_service,

[tim (not reviewing), 2011/01/04 14:32:47]

can you distinguish / explain why multiple ctors are needed? (see
http://google-styleguide.googlecode.com/svn/trunk/cppguide.xml?showone=Functi....
 Sometimes I prefer a named factory method vs second ctor (i.e.
TabNodePoolWithMachineTag, maybe not here though).

[Nicolas Zea, 2011/01/06 01:14:13]

Done.

+                const std::string& current_machine_tag);
+
+    // Add a previously allocated tab sync node to our pool. Increases the size
+    // of tab_syncid_pool_ by one and marks the new tab node as free.
+    // Note: this should only be called when we discover tab sync nodes from
+    // previous sessions, not for freeing tab nodes we created through
+    // GetFreeTabNode (use FreeTabNode below for that).
+    void AddTabNode(int64 sync_id);
+
+    // Returns the sync_id for the next free tab node. If none are available,
+    // creates a new tab node.
+    // Note: We make use of the following "id's"
+    // - a sync_id: an int64 used in |sync_api::InitByIdLookup|
+    // - a tab_id: created by session service, unique to this client
+    // - a tab_node_id: the id for a particular sync tab node. This is used
+    //   to generate the sync tab node tag through:
+    //       tab_tag = StringPrintf("%s_%ui", local_session_tag, tab_node_id);
+    // tab_node_id and sync_id are both unique to a particular sync node. The
+    // difference is that tab_node_id is controlled by the model associator and
+    // is used when creating a new sync node, which returns the sync_id, created
+    // by the sync db.
+    int64 GetFreeTabNode();
+
+    // Return a tab node to our free pool.
+    // Note: the difference between FreeTabNode and AddTabNode is that
+    // FreeTabNode does not modify the size of |tab_syncid_pool_|, while
+    // AddTabNode increases it by one. In the case of FreeTabNode, the size of
+    // the |tab_syncid_pool_| should always be equal to the amount of tab nodes
+    // associated with this machine.
+    void FreeTabNode(int64 sync_id);
+
+    // Clear tab pool.
+    inline void clear() { tab_syncid_pool_.clear(); }
+
+    // Return the number of tab nodes this client currently has allocated
+    // (including both free and used nodes)
+    inline size_t capacity() const { return tab_syncid_pool_.size(); }
+
+    // Return empty status (all tab nodes are in use).
+    inline bool empty() const { return tab_pool_fp_ == -1; }
+
+    // Return full status (no tab nodes are in use).
+    inline bool full() {
+      return tab_pool_fp_ == static_cast<int64>(tab_syncid_pool_.size())-1;
+    }
+
+    inline void set_machine_tag(const std::string& machine_tag) {
+      machine_tag_ = machine_tag;
+    }
+  private:

[tim (not reviewing), 2011/01/04 14:32:47]

nit - indent

[Nicolas Zea, 2011/01/06 01:14:13]

Done.

+    // Pool of all available syncid's for tab's we have created.
+    std::vector<int64> tab_syncid_pool_;
+
+    // Free pointer for tab pool. Only those node id's, up to and including the
+    // one indexed by the free pointer, are valid and free. The rest of the
+    // |tab_syncid_pool_| is invalid because the nodes are in use.
+    // To get the next free node, use tab_syncid_pool_[tab_pool_fp_--].
+    int64 tab_pool_fp_;
+
+    // The machiine tag associated with this tab pool. Used in the title of new
+    // sync nodes.
+    std::string machine_tag_;
+
+    // Our sync service profile (for making changes to the sync db)
+    ProfileSyncService* sync_service_;
+
+    DISALLOW_COPY_AND_ASSIGN(TabNodePool);
+  };
+
+  // Datatypes for accessing local tab data.
+  typedef std::map<SessionID::id_type, TabLinks> TabLinksMap;
+
+  // Delete all foreign session/window/tab objects allocated dynamically.
+  // This is comprised of ForeignSession*, IDToSessionTabMap*, and any orphaned
+  // SessionTab*'s.
+  void DeleteForeignSessions();
+
+  // Determine if a window is of a type we're interested in syncing.
+  static bool ShouldSyncWindowType(const Browser::Type& type);
+
+  // Build a sync tag from tab_node_id.
+  static inline std::string TabIdToTag(
+      const std::string machine_tag,
+      size_t tab_node_id) {
+    return StringPrintf("%s %lu",
+        machine_tag.c_str(), static_cast<unsigned long>(tab_node_id));
+  }
+
   // Initializes the tag corresponding to this machine.
-  // Note: creates a syncable::BaseTransaction.
-  void InitializeCurrentMachineTag();
+  void InitializeCurrentMachineTag(sync_api::WriteTransaction* trans);
 
-  // Populates the navigation portion of the session specifics.
-  void PopulateSessionSpecificsNavigation(const TabNavigation* navigation,
-      sync_pb::TabNavigation* tab_navigation);
+  // Updates the server data based upon the current client session.  If no node
+  // corresponding to this machine exists in the sync model, one is created.
+  void UpdateSyncModelDataFromClient();
 
-  // Populates the tab portion of the session specifics.
-  void PopulateSessionSpecificsTab(const SessionTab* tab,
-      sync_pb::SessionTab* session_tab);
+  // Pulls the current sync model from the sync database and returns true upon
+  // update of the client model. Will associate any foreign sessions as well as
+  // keep track of any local tab nodes, adding them to our free tab node pool.
+  bool UpdateAssociationsFromSyncModel(const sync_api::ReadNode& root,
+                                       const sync_api::BaseTransaction* trans);
 
-  // Populates the window portion of the session specifics.
-  void PopulateSessionSpecificsWindow(const SessionWindow* window,
-      sync_pb::SessionWindow* session_window);
+  // Fills a tab sync node with data from a TabContents object.
+  // (from a local navigation event)
+  bool WriteTabContentsToSyncModel(const TabContents& tab,
+                                   const int64 sync_id,
+                                   sync_api::WriteTransaction* trans);
 
-  // Specifies whether the window has tabs to sync.  The new tab page does not
-  // count.  If no tabs to sync, it returns true, otherwise false;
-  bool WindowHasNoTabsToSync(const SessionWindow* window);
+  // Used to populate a session window from the session specifics window
+  // provided. Tracks any foreign session data created through |tracker|.
+  static void PopulateSessionWindowFromSpecifics(
+      std::string foreign_session_tag,
+      const sync_pb::SessionWindow& window,
+      const int64 mtime,
+      SessionWindow* session_window,
+      ForeignSessionTracker* tracker);
 
+  // Used to populate a session tab from the session specifics tab provided.
+  static void PopulateSessionTabFromSpecifics(const sync_pb::SessionTab& tab,
+                                              const int64 mtime,
+                                              SessionTab* session_tab);
+
+  // Used to populate a session tab from the session specifics tab provided.
+  static void AppendSessionTabNavigation(
+     const sync_pb::TabNavigation& navigation,
+     std::vector<TabNavigation>* navigations);
+
+  // Populates the navigation portion of the session specifics.
+  static void PopulateSessionSpecificsNavigation(
+     const TabNavigation* navigation,
+     sync_pb::TabNavigation* tab_navigation);
+
+  // Returns the session service from |sync_service_|.
+  SessionService* GetSessionService();
+
   // Internal method used in the callback to obtain the current session.
   // We don't own |windows|.
   void OnGotSession(int handle, std::vector<SessionWindow*>* windows);
 
-  // Used to populate a session tab from the session specifics tab provided.
-  void AppendSessionTabNavigation(std::vector<TabNavigation>* navigations,
-      const sync_pb::TabNavigation* navigation);
+  // Populate a session specifics header from a list of SessionWindows
+  void PopulateSessionSpecificsHeader(
+      const std::vector<SessionWindow*>& windows,
+      sync_pb::SessionHeader* header_s);
 
-  // Used to populate a session tab from the session specifics tab provided.
-  void PopulateSessionTabFromSpecifics(SessionTab* session_tab,
-      const sync_pb::SessionTab* tab, SessionID id);
+  // Populates the window portion of the session specifics.
+  void PopulateSessionSpecificsWindow(const SessionWindow& window,
+                                      sync_pb::SessionWindow* session_window);
 
-  // Used to populate a session window from the session specifics window
-  // provided.
-  void PopulateSessionWindowFromSpecifics(SessionWindow* session_window,
-      const sync_pb::SessionWindow* window);
+  // Syncs all the tabs in |window| with the local sync db. Will allocate tab
+  // nodes if needed.
+  bool SyncLocalWindowToSyncModel(const SessionWindow& window);
 
-  // Updates the current session on the server.  Creates a node for this machine
-  // if there is not one already.
-  bool UpdateSyncModel(sync_pb::SessionSpecifics* session_data,
-                    sync_api::WriteTransaction* trans,
-                    const sync_api::ReadNode* root);
-  // Stores the machine tag.
+  // Fills a tab sync node with data from a SessionTab object.
+  // (from ReadCurrentSessions)
+  bool WriteSessionTabToSyncModel(const SessionTab& tab,
+                                  const int64 sync_id,
+                                  sync_api::WriteTransaction* trans);
+
+  // Populates the tab portion of the session specifics.
+  void PopulateSessionSpecificsTab(const SessionTab& tab,
+                                   sync_pb::SessionTab* session_tab);
+
+  // Local client name.
   std::string current_machine_tag_;
 
-  // Stores the current set of foreign session specifics.
-  // Used by ForeignSessionHandler through |GetSessionData|.
-  // Built by |QuerySyncModel| via |UpdateFromSyncModel|.
-  std::vector<const sync_pb::SessionSpecifics*> specifics_;
+  // Pool of all used/available sync nodes associated with tabs.
+  TabNodePool tab_pool_;
 
+  // SyncID for the sync node containing all the window information for this
+  // client.
+  int64 local_session_syncid_;
+
+  // Mapping of current open (local) tabs to their sync identifiers.
+  TabLinksMap tab_map_;
+
+  ForeignSessionTracker foreign_session_tracker_;
+
   // Weak pointer.
   ProfileSyncService* sync_service_;