Do not submit: high level overview patch.

chrome/browser/sessions/session_service.cc

Index: chrome/browser/sessions/session_service.cc
diff --git a/chrome/browser/sessions/session_service.cc b/chrome/browser/sessions/session_service.cc
index 0cace940b9e37c8f6268e807077df7b5a6e7a1a3..bedbb000fdb3912312406540deb2cfef24971fc9 100644
--- a/chrome/browser/sessions/session_service.cc
+++ b/chrome/browser/sessions/session_service.cc
@@ -25,6 +25,7 @@
 #include "chrome/browser/sessions/session_restore.h"
 #include "chrome/browser/sessions/session_tab_helper.h"
 #include "chrome/browser/sessions/session_types.h"
+#include "chrome/browser/sync/glue/synced_tab_delegate.h"
 #include "chrome/browser/ui/browser_iterator.h"
 #include "chrome/browser/ui/browser_list.h"
 #include "chrome/browser/ui/browser_tabstrip.h"
@@ -50,6 +51,7 @@ using base::Time;
 using content::NavigationEntry;
 using content::WebContents;
 using sessions::SerializedNavigationEntry;
+using browser_sync::SyncedTabDelegate;
 
 // Identifier for commands written to file.
 static const SessionCommand::id_type kCommandSetTabWindow = 0;
@@ -79,6 +81,7 @@ static const SessionCommand::id_type kCommandWindowClosed = 17;
 static const SessionCommand::id_type kCommandSetTabUserAgentOverride = 18;
 static const SessionCommand::id_type kCommandSessionStorageAssociated = 19;
 static const SessionCommand::id_type kCommandSetActiveWindow = 20;
+static const SessionCommand::id_type kCommandSetTabSessionSyncId = 21;
 
 // Every kWritesPerReset commands triggers recreating the file.
 static const int kWritesPerReset = 250;
@@ -480,6 +483,15 @@ void SessionService::SetTabUserAgentOverride(
       kCommandSetTabUserAgentOverride, tab_id.id(), user_agent_override));
 }
 
+void SessionService::SetTabSessionSyncId(const SessionID& window_id,
+                                         const SessionID& tab_id,
+                                         const int64& sync_id) {
+  if (!ShouldTrackChangesToWindow(window_id))
+    return;
+  ScheduleCommand(CreateSetTabSessionSyncIdCommand(
+      kCommandSetTabSessionSyncId, tab_id.id(), sync_id));
+}
+
 CancelableTaskTracker::TaskId SessionService::GetLastSession(
     const SessionCallback& callback,
     CancelableTaskTracker* tracker) {
@@ -518,6 +530,9 @@ void SessionService::Init() {
   registrar_.Add(
       this, chrome::NOTIFICATION_TAB_CONTENTS_APPLICATION_EXTENSION_CHANGED,
       content::NotificationService::AllSources());
+  registrar_.Add(this,
+                 chrome::NOTIFICATION_SESSION_SYNC_ID_GENERATED,
+                 content::NotificationService::AllSources());
 
   BrowserList::AddObserver(this);
 }
@@ -680,6 +695,13 @@ void SessionService::Observe(int type,
                              extension_tab_helper->extension_app()->id());
       }
       break;
+
+    }
+    case chrome::NOTIFICATION_SESSION_SYNC_ID_GENERATED: {
+      content::Details<const SyncedTabDelegate> tab(details);
+      SetTabSessionSyncId(
+          tab->GetWindowId(), tab->GetSessionId(), tab->GetSyncSessionId());
+      break;
     }
 
     default:
@@ -1261,6 +1283,15 @@ bool SessionService::CreateTabsAndWindows(
         break;
       }
 
+      case kCommandSetTabSessionSyncId: {
+        SessionID::id_type tab_id;
+        int64 sync_id = -1;
+        if (!RestoreSetTabSessionSyncIdCommand(*command, &tab_id, &sync_id)) {
+        }
+        GetTab(tab_id, tabs)->sync_session_id = sync_id;
+        break;
+      }
+
       default:
         VLOG(1) << "Failed reading an unknown command " << command->id();
         return true;
@@ -1311,6 +1342,10 @@ void SessionService::BuildCommandsForTab(const SessionID& window_id,
         CreateSetTabUserAgentOverrideCommand(
             kCommandSetTabUserAgentOverride, session_id.id(), ua_override));
   }
+  const int64 sync_id =
+      SessionTabHelper::FromWebContents(tab)->GetSessionSyncId();
+  commands->push_back(CreateSetTabSessionSyncIdCommand(
+      kCommandSetTabSessionSyncId, session_id.id(), sync_id));
 
   for (int i = min_index; i < max_index; ++i) {
     const NavigationEntry* entry = (i == pending_index) ?