Fix more disabled MSVC warnings, base/ edition.

base/metrics/histogram_base.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 "base/metrics/histogram_base.h"
 
 #include <climits>
 
 #include "base/json/json_string_value_serializer.h"
 #include "base/logging.h"
@@ skipping 91 matching lines @@
   int64 sum;
   scoped_ptr<ListValue> buckets(new ListValue());
   GetCountAndBucketData(&count, &sum, buckets.get());
   scoped_ptr<DictionaryValue> parameters(new DictionaryValue());
   GetParameters(parameters.get());
 
   JSONStringValueSerializer serializer(output);
   DictionaryValue root;
   root.SetString("name", histogram_name());
   root.SetInteger("count", count);
-  root.SetDouble("sum", sum);
+  root.SetDouble("sum", static_cast<double>(sum));
   root.SetInteger("flags", flags());
   root.Set("params", parameters.release());
   root.Set("buckets", buckets.release());
   root.SetInteger("pid", GetCurrentProcId());
   serializer.Serialize(root);
 }
 
 void HistogramBase::WriteAsciiBucketGraph(double current_size,
                                           double max_size,
                                           std::string* output) const {
@@ skipping 19 matching lines @@
   return result;
 }
 
 void HistogramBase::WriteAsciiBucketValue(Count current,
                                           double scaled_sum,
                                           std::string* output) const {
   StringAppendF(output, " (%d = %3.1f%%)", current, current/scaled_sum);
 }
 
 }  // namespace base