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

sync/internal_api/write_node.cc

 // Copyright (c) 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.
 
 #include "sync/internal_api/public/write_node.h"
 
 #include <stdint.h>
 
 #include "base/strings/string_util.h"
 #include "base/strings/utf_string_conversions.h"
@@ skipping 356 matching lines @@
       // Client tags are immutable and must be paired with the ID.
       // If a server update comes down with an ID and client tag combo,
       // and it already exists, always overwrite it and store only one copy.
       // We have to undelete entries because we can't disassociate IDs from
       // tags and updates.
 
       existing_entry->PutNonUniqueName(dummy);
       existing_entry->PutParentId(parent_id);
     }  // Else just reuse the existing entry.
     entry_ = existing_entry.release();
+    if (!DecryptIfNecessary())
+      return INIT_FAILED_DECRYPT_EXISTING_ENTRY;
   } else {
     entry_ = new syncable::MutableEntry(transaction_->GetWrappedWriteTrans(),
                                         syncable::CREATE,
                                         model_type, parent_id, dummy);
   }
 
   if (!entry_->good())
     return INIT_FAILED_COULD_NOT_CREATE_ENTRY;
 
   // Has no impact if the client tag is already set.
@@ skipping 80 matching lines @@
   syncable::Id predecessor_id =
       predecessor ? predecessor->GetSyncId() : syncable::Id();
   return entry_->PutPredecessor(predecessor_id);
 }
 
 void WriteNode::MarkForSyncing() {
   syncable::MarkForSyncing(entry_);
 }
 
 }  // namespace syncer