[Sync] Replace uses of ObserverListThreadSafe with WeakHandles

chrome/browser/sync/syncable/directory_manager.h

Index: chrome/browser/sync/syncable/directory_manager.h
diff --git a/chrome/browser/sync/syncable/directory_manager.h b/chrome/browser/sync/syncable/directory_manager.h
index 4a7316fc81ae19412196e963a7b5b78b4d826472..243000ba84eb7b7de501b43a9add87681ff790eb 100644
--- a/chrome/browser/sync/syncable/directory_manager.h
+++ b/chrome/browser/sync/syncable/directory_manager.h
@@ -22,6 +22,7 @@
 #include "chrome/browser/sync/syncable/dir_open_result.h"
 #include "chrome/browser/sync/syncable/syncable.h"
 #include "chrome/browser/sync/util/cryptographer.h"
+#include "chrome/browser/sync/util/weak_handle.h"
 
 namespace sync_api { class BaseTransaction; }
 namespace syncable { class BaseTransaction; }
@@ -45,8 +46,10 @@ class DirectoryManager {
   // common case.  Does not take ownership of |delegate|, which must
   // be non-NULL.  Starts sending events to |delegate| if the returned
   // result is true.  Note that events to |delegate| may be sent from
-  // *any* thread.
-  bool Open(const std::string& name, DirectoryChangeDelegate* delegate);
+  // *any* thread.  |transaction_observer| must be initialized.
+  bool Open(const std::string& name, DirectoryChangeDelegate* delegate,
+            const browser_sync::WeakHandle<TransactionObserver>&
+                transaction_observer);
 
   // Marks a directory as closed and stops sending events to the
   // delegate.  It might take a while until all the file handles and
@@ -74,8 +77,12 @@ class DirectoryManager {
     return cryptographer_.get();
   }
 
-  DirOpenResult OpenImpl(const std::string& name, const FilePath& path,
-                         DirectoryChangeDelegate* delegate, bool* was_open);
+  DirOpenResult OpenImpl(
+      const std::string& name, const FilePath& path,
+      DirectoryChangeDelegate* delegate,
+      const browser_sync::WeakHandle<TransactionObserver>&
+          transaction_observer,
+      bool* was_open);
 
   // Helpers for friend class ScopedDirLookup:
   friend class ScopedDirLookup;