[Sync] Implement MemoryDumpProvider.

components/sync/base/unique_position.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 "components/sync/base/unique_position.h"
 
 #include <algorithm>
 #include <limits>
 
 #include "base/logging.h"
 #include "base/rand_util.h"
 #include "base/stl_util.h"
 #include "base/strings/string_number_conversions.h"
+#include "base/trace_event/memory_usage_estimator.h"
 #include "components/sync/protocol/unique_position.pb.h"
 #include "third_party/zlib/zlib.h"
 
 namespace syncer {
 
 const size_t UniquePosition::kSuffixLength = 28;
 const size_t UniquePosition::kCompressBytesThreshold = 128;
 
 // static.
 bool UniquePosition::IsValidSuffix(const std::string& suffix) {
@@ skipping 583 matching lines @@
         // this is not the highest possible count.
         return false;
       }
     }
   }
   // We don't bother looking for the existence or checking the validity of
   // any partial blocks.  There's no way they could be invalid anyway.
   return true;
 }
 
+size_t UniquePosition::EstimateMemoryUsage() const {
+  using base::trace_event::EstimateMemoryUsage;
+  return EstimateMemoryUsage(compressed_);
+}
+
 }  // namespace syncer