[Sync] Fix crash in GCP when adding encrypted entry that already exists.

sync/internal_api/public/write_node.h

 // Copyright 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef SYNC_INTERNAL_API_PUBLIC_WRITE_NODE_H_
 #define SYNC_INTERNAL_API_PUBLIC_WRITE_NODE_H_
 
 #include <stddef.h>
 #include <stdint.h>
 
@@ skipping 31 matching lines @@
 class SYNC_EXPORT WriteNode : public BaseNode {
  public:
   enum InitUniqueByCreationResult {
     INIT_SUCCESS,
     // The tag passed into this method was empty.
     INIT_FAILED_EMPTY_TAG,
     // The constructor for a new MutableEntry with the specified data failed.
     INIT_FAILED_COULD_NOT_CREATE_ENTRY,
     // Setting the predecessor failed
     INIT_FAILED_SET_PREDECESSOR,
+    // Found existing entry, but was unable to decrypt.
+    INIT_FAILED_DECRYPT_EXISTING_ENTRY,
   };
 
   // Create a WriteNode using the given transaction.
   explicit WriteNode(WriteTransaction* transaction);
   ~WriteNode() override;
 
   // A client must use one (and only one) of the following Init variants to
   // populate the node.
 
   // BaseNode implementation.
@@ skipping 110 matching lines @@
 
   // The sync API transaction that is the parent of this node.
   WriteTransaction* transaction_;
 
   DISALLOW_COPY_AND_ASSIGN(WriteNode);
 };
 
 }  // namespace syncer
 
 #endif  // SYNC_INTERNAL_API_PUBLIC_WRITE_NODE_H_