[Sync] Introduce SyncedSessionWindow type.

components/sync_sessions/synced_session.h

Index: components/sync_sessions/synced_session.h
diff --git a/components/sync_sessions/synced_session.h b/components/sync_sessions/synced_session.h
index e0defd96623490463ba4a8182e13dae483b711c4..c3471ae20d435c83e3fe5673943f2d264a99beef 100644
--- a/components/sync_sessions/synced_session.h
+++ b/components/sync_sessions/synced_session.h
@@ -16,12 +16,26 @@
 #include "components/sessions/core/session_types.h"
 #include "components/sync/protocol/session_specifics.pb.h"
 
-namespace sessions {
-struct SessionWindow;
-}
-
 namespace sync_sessions {
 
+// A Sync wrapper for a SessionWindow.
+struct SyncedSessionWindow {
+  SyncedSessionWindow();
+  ~SyncedSessionWindow();
+
+  // Convert this object into its sync protocol buffer equivalent.
+  sync_pb::SessionWindow ToSessionWindowProto() const;
+
+  // Type of the window. See session_specifics.proto.
+  sync_pb::SessionWindow::BrowserType window_type;
+
+  // The SessionWindow this object wraps.
+  sessions::SessionWindow wrapped_window;
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(SyncedSessionWindow);
+};
+
 // Defines a synced session for use by session sync. A synced session is a
 // list of windows along with a unique session identifer (tag) and meta-data
 // about the device being synced.
@@ -55,8 +69,7 @@ struct SyncedSession {
   base::Time modified_time;
 
   // Map of windows that make up this session.
-  std::map<SessionID::id_type, std::unique_ptr<sessions::SessionWindow>>
-      windows;
+  std::map<SessionID::id_type, std::unique_ptr<SyncedSessionWindow>> windows;
 
   // A tab node id is part of the identifier for the sync tab objects. Tab node
   // ids are not used for interacting with the model/browser tabs. However, when
@@ -95,7 +108,7 @@ struct SyncedSession {
 
   // Convert this object to its protocol buffer equivalent. Shallow conversion,
   // does not create SessionTab protobufs.
-  sync_pb::SessionHeader ToSessionHeader() const;
+  sync_pb::SessionHeader ToSessionHeaderProto() const;
 
  private:
   DISALLOW_COPY_AND_ASSIGN(SyncedSession);