Adding checks to guard against buffer overruns in QuotaFileIO::Write and base::FileUtilProxy::Write

base/file_util_proxy.h

 // Copyright (c) 2011 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 BASE_FILE_UTIL_PROXY_H_
 #define BASE_FILE_UTIL_PROXY_H_
 
 #include <vector>
 
 #include "base/base_export.h"
@@ skipping 150 matching lines @@
   static bool Read(
       scoped_refptr<MessageLoopProxy> message_loop_proxy,
       PlatformFile file,
       int64 offset,
       int bytes_to_read,
       ReadCallback* callback);
 
   // Writes to a file. If |offset| is greater than the length of the file,
   // |false| is returned. On success, the file pointer is moved to position
   // |offset + bytes_to_write| in the file. The callback can be NULL.
+  // |bytes_to_write| must be greater than zero.
   static bool Write(
       scoped_refptr<MessageLoopProxy> message_loop_proxy,
       PlatformFile file,
       int64 offset,
       const char* buffer,
       int bytes_to_write,
       WriteCallback* callback);
 
   // Touches a file. The callback can be NULL.
   static bool Touch(
@@ skipping 35 matching lines @@
       PlatformFile file,
       StatusCallback* callback);
 
  private:
   DISALLOW_IMPLICIT_CONSTRUCTORS(FileUtilProxy);
 };
 
 }  // namespace base
 
 #endif  // BASE_FILE_UTIL_PROXY_H_