Added classes to enable session sync functionality.

chrome/browser/sessions/session_types.h

Index: chrome/browser/sessions/session_types.h
diff --git a/chrome/browser/sessions/session_types.h b/chrome/browser/sessions/session_types.h
index 2ea075789ce1cafc8d25ef183ac3cb8e35b0bd4b..07dbae4f68af35b485c431268db231df01ab3056 100644
--- a/chrome/browser/sessions/session_types.h
+++ b/chrome/browser/sessions/session_types.h
@@ -88,7 +88,7 @@ class TabNavigation {
   // This is used when determining the selected TabNavigation and only useful
   // by BaseSessionService and SessionService.
   void set_index(int index) { index_ = index; }
-  int index() { return index_; }
+  int index() const { return index_; }
 
  private:
   friend class BaseSessionService;
@@ -189,4 +189,16 @@ struct SessionWindow {
   DISALLOW_COPY_AND_ASSIGN(SessionWindow);
 };
 
+// Defines a foreign session for session sync.  A foreign session is a session
+// on a remote chrome instance.
+struct ForeignSession {
+  ForeignSession();
+  ~ForeignSession();
+
+  // Unique tag for each session.
+  std::string foreign_tession_tag;
+  std::vector<SessionWindow*> windows;
+};
+
 #endif  // CHROME_BROWSER_SESSIONS_SESSION_TYPES_H_
+