[Sync] Add support for enabling session sync remotely.

chrome/browser/sync/profile_sync_service.h

Index: chrome/browser/sync/profile_sync_service.h
diff --git a/chrome/browser/sync/profile_sync_service.h b/chrome/browser/sync/profile_sync_service.h
index d32b7371a1c973b1d3b6a3e03b930adb40c30ad8..7e0a69717e19b3b5703c867236d56606757ffd77 100644
--- a/chrome/browser/sync/profile_sync_service.h
+++ b/chrome/browser/sync/profile_sync_service.h
@@ -164,8 +164,8 @@ class ProfileSyncService : public browser_sync::SyncFrontend,
   // makes the data type controller available for use, it does not
   // enable or activate the synchronization of the data type (see
   // ActivateDataType).  Takes ownership of the pointer.
-  void RegisterDataTypeController(
-      browser_sync::DataTypeController* data_type_controller);
+  virtual void RegisterDataTypeController(
+      browser_sync::DataTypeController* data_type_controller) OVERRIDE;
 
   // Returns the session model associator associated with this type, but only if
   // the associator is running.  If it is doing anything else, it will return
@@ -413,14 +413,14 @@ class ProfileSyncService : public browser_sync::SyncFrontend,
   // the user).  See class comment for more on what it means for a datatype
   // to be Preferred.
   virtual void GetPreferredDataTypes(
-      syncable::ModelTypeSet* preferred_types) const;
+      syncable::ModelTypeSet* preferred_types) const OVERRIDE;
 
   // Gets the set of all data types that could be allowed (the set that
   // should be advertised to the user).  These will typically only change
   // via a command-line option.  See class comment for more on what it means
   // for a datatype to be Registered.
   virtual void GetRegisteredDataTypes(
-      syncable::ModelTypeSet* registered_types) const;
+      syncable::ModelTypeSet* registered_types) const OVERRIDE;
 
   // Checks whether the Cryptographer is ready to encrypt and decrypt updates
   // for sensitive data types. Caller must be holding a