[update_engine] Fix file creation mask to be 0600

extent_writer.h

 // Copyright (c) 2009 The Chromium OS 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 CHROMEOS_PLATFORM_UPDATE_ENGINE_EXTENT_WRITER_H__
 #define CHROMEOS_PLATFORM_UPDATE_ENGINE_EXTENT_WRITER_H__
 
 #include <vector>
 #include "base/logging.h"
 #include "update_engine/update_metadata.pb.h"
@@ skipping 48 matching lines @@
     extents_ = extents;
     return true;
   }
   bool Write(const void* bytes, size_t count);
   bool EndImpl() {
     return true;
   }
 
  private:
   int fd_;
-  
+
   size_t block_size_;
   // Bytes written into next_extent_index_ thus far
   uint64_t extent_bytes_written_;
   std::vector<Extent> extents_;
   // The next call to write should correspond to extents_[next_extent_index_]
   std::vector<Extent>::size_type next_extent_index_;
 };
 
 // Takes an underlying ExtentWriter to which all operations are delegated.
 // When End() is called, ZeroPadExtentWriter ensures that the total number
@@ skipping 32 matching lines @@
 
  private:
   ExtentWriter* underlying_extent_writer_;  // The underlying ExtentWriter.
   size_t block_size_;
   size_t bytes_written_mod_block_size_;
 };
 
 }  // namespace chromeos_update_engine
 
 #endif  // CHROMEOS_PLATFORM_UPDATE_ENGINE_EXTENT_WRITER_H__