2 files changed, 19 insertions, 3 deletions
diff --git a/chrome/browser/sync/syncable/syncable.cc b/chrome/browser/sync/syncable/syncable.cc
index d5ce7a6..fdd379c 100755
--- a/chrome/browser/sync/syncable/syncable.cc
+++ b/chrome/browser/sync/syncable/syncable.cc
@@ -1142,8 +1142,8 @@ bool MutableEntry::Put(IdField field, const Id& value) {
       if (!dir()->ReindexId(kernel_, value))
         return false;
     } else if (PARENT_ID == field) {
-      dir()->ReindexParentId(kernel_, value);
-      PutPredecessor(Id());
+      PutParentIdPropertyOnly(value);  // Makes sibling order inconsistent.
+      PutPredecessor(Id());  // Fixes up the sibling order inconsistency.
     } else {
       kernel_->put(field, value);
     }
@@ -1152,6 +1152,10 @@ bool MutableEntry::Put(IdField field, const Id& value) {
   return true;
 }
 
+void MutableEntry::PutParentIdPropertyOnly(const Id& parent_id) {
+  dir()->ReindexParentId(kernel_, parent_id);
+}
+
 bool MutableEntry::Put(BaseVersion field, int64 value) {
   DCHECK(kernel_);
   if (kernel_->ref(field) != value) {
@@ -1269,6 +1273,7 @@ bool MutableEntry::PutPredecessor(const Id& predecessor_id) {
   return true;
 }
 
+
 ///////////////////////////////////////////////////////////////////////////
 // High-level functions
 
diff --git a/chrome/browser/sync/syncable/syncable.h b/chrome/browser/sync/syncable/syncable.h
index 0fe199e..be091d0 100755
--- a/chrome/browser/sync/syncable/syncable.h
+++ b/chrome/browser/sync/syncable/syncable.h
@@ -442,6 +442,18 @@ class MutableEntry : public Entry {
   // TODO(chron): Remove some of these unecessary return values.
   bool Put(Int64Field field, const int64& value);
   bool Put(IdField field, const Id& value);
+
+  // Do a simple property-only update if the PARENT_ID field.  Use with caution.
+  //
+  // The normal Put(IS_PARENT) call will move the item to the front of the
+  // sibling order to maintain the linked list invariants when the parent
+  // changes.  That's usually what you want to do, but it's inappropriate
+  // when the caller is trying to change the parent ID of a the whole set
+  // of children (e.g. because the ID changed during a commit).  For those
+  // cases, there's this function.  It will corrupt the sibling ordering
+  // if you're not careful.
+  void PutParentIdPropertyOnly(const Id& parent_id);
+
   bool Put(StringField field, const std::string& value);
   bool Put(BaseVersion field, int64 value);
 
@@ -474,7 +486,6 @@ class MutableEntry : public Entry {
   }
 
  protected:
-
   template <typename FieldType, typename ValueType>
   inline bool PutField(FieldType field, const ValueType& value) {
     DCHECK(kernel_);