[sync] WebContentsObserver based sessions notifications

components/sync_sessions/tab_node_pool.h

 // Copyright 2014 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.
 
 #ifndef COMPONENTS_SYNC_SESSIONS_TAB_NODE_POOL_H_
 #define COMPONENTS_SYNC_SESSIONS_TAB_NODE_POOL_H_
 
 #include <stddef.h>
 
 #include <map>
@@ skipping 14 matching lines @@
 //       tab_tag = StringPrintf("%s %d", local_session_tag, tab_node_id);
 //
 // A sync node can be in one of the two states:
 // 1. Associated   : Sync node is used and associated with a tab.
 // 2. Free         : Sync node is unused.
 
 class TabNodePool {
  public:
   TabNodePool();
   ~TabNodePool();
-  enum InvalidTab { kInvalidTabID = -1 };
 
   // If free nodes > kFreeNodesHighWatermark, delete all free nodes until
   // free nodes <= kFreeNodesLowWatermark.
   static const size_t kFreeNodesLowWatermark;
 
   // Maximum limit of FreeNodes allowed on the client.
   static const size_t kFreeNodesHighWatermark;
 
   static const int kInvalidTabNodeID;
 
@@ skipping 65 matching lines @@
   // The maximum used tab_node id for a sync node. A new sync node will always
   // be created with max_used_tab_node_id_ + 1.
   int max_used_tab_node_id_;
 
   DISALLOW_COPY_AND_ASSIGN(TabNodePool);
 };
 
 }  // namespace sync_sessions
 
 #endif  // COMPONENTS_SYNC_SESSIONS_TAB_NODE_POOL_H_