Harden allocator for file-backed memory.

components/metrics/file_metrics_provider.h

 // Copyright 2016 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.
 
 #ifndef COMPONENTS_METRICS_FILE_METRICS_PROVIDER_H_
 #define COMPONENTS_METRICS_FILE_METRICS_PROVIDER_H_
 
 #include <list>
 #include <memory>
 #include <string>
@@ skipping 111 matching lines @@
 
     // System could not map file into memory.
     ACCESS_RESULT_SYSTEM_MAP_FAILURE,
 
     // File had invalid contents.
     ACCESS_RESULT_INVALID_CONTENTS,
 
     // File could not be opened.
     ACCESS_RESULT_NO_OPEN,
 
+    // File contents were internally deleted.
+    ACCESS_RESULT_MEMORY_DELETED,
+
     ACCESS_RESULT_MAX
   };
 
   // Information about sources being monitored; defined and used exclusively
   // inside the .cc file.
   struct SourceInfo;
   using SourceInfoList = std::list<std::unique_ptr<SourceInfo>>;
 
   // Looks for the next file to read within a directory. Returns true if a
   // file was found. This is part of CheckAndMapNewMetricSourcesOnTaskRunner
@@ skipping 57 matching lines @@
 
   base::ThreadChecker thread_checker_;
   base::WeakPtrFactory<FileMetricsProvider> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(FileMetricsProvider);
 };
 
 }  // namespace metrics
 
 #endif  // COMPONENTS_METRICS_FILE_METRICS_PROVIDER_H_