Fix memory leak in PrefMetricsService

chrome/browser/prefs/pref_metrics_service.cc

 // Copyright 2013 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 "chrome/browser/prefs/pref_metrics_service.h"
 
 #include "base/bind.h"
 #include "base/command_line.h"
 #include "base/json/json_string_value_serializer.h"
 #include "base/metrics/histogram.h"
@@ skipping 336 matching lines @@
   return hash_pref_path;
 }
 
 std::string PrefMetricsService::GetHashedPrefValue(
     const char* path,
     const base::Value* value) {
   DCHECK(value);
 
   // Dictionary values may contain empty lists and sub-dictionaries. Create
   // a deep copy with those stripped to make the hash more stable.
-  DictionaryValue* dict_value =
-      static_cast<DictionaryValue*>(const_cast<Value*>(value));
-  if (dict_value)
-    value = dict_value->DeepCopyWithoutEmptyChildren();
+  scoped_ptr<DictionaryValue> dict_value;
+  if (value->IsType(Value::TYPE_DICTIONARY)) {
+    dict_value.reset(static_cast<const DictionaryValue*>(value)
+                         ->DeepCopyWithoutEmptyChildren());
+    value = dict_value.get();
+  }
 
   std::string string_to_hash(device_id_);
   string_to_hash.append(path);
   JSONStringValueSerializer serializer(&string_to_hash);
   serializer.Serialize(*value);
 
   crypto::HMAC hmac(crypto::HMAC::SHA256);
   unsigned char digest[kSHA256DigestSize];
   if (!hmac.Init(pref_hash_seed_) ||
       !hmac.Sign(string_to_hash, digest, kSHA256DigestSize)) {
@@ skipping 51 matching lines @@
 }
 
 bool PrefMetricsService::Factory::ServiceIsNULLWhileTesting() const {
   return false;
 }
 
 content::BrowserContext* PrefMetricsService::Factory::GetBrowserContextToUse(
     content::BrowserContext* context) const {
   return chrome::GetBrowserContextRedirectedInIncognito(context);
 }