sync: Count nodes more efficiently

sync/syncable/directory.h

Index: sync/syncable/directory.h
diff --git a/sync/syncable/directory.h b/sync/syncable/directory.h
index 61c55224911d4b894ab0960ee73fec0f686691b2..1f787f28543ef0a2a9a4e57491f26001fec75424 100644
--- a/sync/syncable/directory.h
+++ b/sync/syncable/directory.h
@@ -321,6 +321,9 @@ class SYNC_EXPORT Directory {
   bool GetChildHandlesByHandle(BaseTransaction*, int64 handle,
       ChildHandles* result);
 
+  // Counts all items under the given node, including the node itself.
+  int GetTotalNodeCount(BaseTransaction*, EntryKernel* kernel_) const;
+
   // Returns true iff |id| has children.
   bool HasChildren(BaseTransaction* trans, const Id& id);
 
@@ -454,6 +457,12 @@ class SYNC_EXPORT Directory {
   bool SafeToPurgeFromMemory(WriteTransaction* trans,
                              const EntryKernel* const entry) const;
 
+  // A helper used by GetTotalNodeCount.
+  void GetChildSetForKernel(
+      BaseTransaction*,
+      EntryKernel* kernel_,
+      std::deque<const OrderedChildSet*>* child_sets) const;
+
   Directory& operator = (const Directory&);
 
  public: