sync: Test and improve bookmark performance

sync/syncable/syncable_write_transaction.cc

 // 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.
 
 #include "sync/syncable/syncable_write_transaction.h"
 
 #include "sync/syncable/directory.h"
 #include "sync/syncable/directory_change_delegate.h"
 #include "sync/syncable/mutable_entry.h"
 #include "sync/syncable/transaction_observer.h"
@@ skipping 22 matching lines @@
 }
 
 void WriteTransaction::SaveOriginal(const EntryKernel* entry) {
   if (!entry) {
     return;
   }
   // Insert only if it's not already there.
   const int64 handle = entry->ref(META_HANDLE);
   EntryKernelMutationMap::iterator it = mutations_.lower_bound(handle);
   if (it == mutations_.end() || it->first != handle) {
-    EntryKernelMutation mutation;
-    mutation.original = *entry;
-    ignore_result(mutations_.insert(it, std::make_pair(handle, mutation)));
+    mutations_[handle].original = *entry;
   }
 }
 
 ImmutableEntryKernelMutationMap WriteTransaction::RecordMutations() {
   directory_->kernel_->transaction_mutex.AssertAcquired();
   for (syncable::EntryKernelMutationMap::iterator it = mutations_.begin();
        it != mutations_.end();) {
     EntryKernel* kernel = directory()->GetEntryByHandle(it->first);
     if (!kernel) {
       NOTREACHED();
@@ skipping 119 matching lines @@
     ENUM_CASE(SYNCAPI);
   };
   NOTREACHED();
   return std::string();
 }
 
 #undef ENUM_CASE
 
 }  // namespace syncable
 }  // namespace syncer