Make base::ReadFileToString() return false on I/O error.

base/file_util.h

 // 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.
 
 // This file contains utility functions for dealing with the local
 // filesystem.
 
 #ifndef BASE_FILE_UTIL_H_
 #define BASE_FILE_UTIL_H_
 
@@ skipping 118 matching lines @@
 // Returns true if the contents of the two files given are equal, false
 // otherwise.  If either file can't be read, returns false.
 BASE_EXPORT bool ContentsEqual(const FilePath& filename1,
                                const FilePath& filename2);
 
 // Returns true if the contents of the two text files given are equal, false
 // otherwise.  This routine treats "\r\n" and "\n" as equivalent.
 BASE_EXPORT bool TextContentsEqual(const FilePath& filename1,
                                    const FilePath& filename2);
 
-// Reads the file at |path| into |contents| and returns true on success.
-// |contents| may be NULL, in which case this function is useful for its
-// side effect of priming the disk cache (could be used for unit tests).
-// The function returns false and the string pointed to by |contents| is
-// cleared when |path| does not exist or if it contains path traversal
-// components ('..').
+// Reads the file at |path| into |contents| and returns true on success and
+// false on error.  For security reasons, a |path| containing path traversal
+// components ('..') is treated as a read error and |contents| is set to empty.
+// In case of I/O error, |contents| holds the data that could be read from the
+// file before the error occurred.
+// |contents| may be NULL, in which case this function is useful for its side
+// effect of priming the disk cache (could be used for unit tests).
 BASE_EXPORT bool ReadFileToString(const FilePath& path, std::string* contents);
 
-// Reads the file at |path| into |contents| and returns true on success.
-// |contents| may be NULL, in which case this function is useful for its
-// side effect of priming the disk cache (could be used for unit tests).
-// The function returns false and the string pointed to by |contents| is
-// cleared when |path| does not exist or if it contains path traversal
-// components ('..').
-// When the file size exceeds |max_size|, the function returns false
-// with |contents| holding the file truncated to |max_size|.
+// Reads the file at |path| into |contents| and returns true on success and
+// false on error.  For security reasons, a |path| containing path traversal
+// components ('..') is treated as a read error and |contents| is set to empty.
+// In case of I/O error, |contents| holds the data that could be read from the
+// file before the error occurred.  When the file size exceeds |max_size|, the
+// function returns false with |contents| holding the file truncated to
+// |max_size|.
+// |contents| may be NULL, in which case this function is useful for its side
+// effect of priming the disk cache (could be used for unit tests).
 BASE_EXPORT bool ReadFileToString(const FilePath& path,
                                   std::string* contents,
                                   size_t max_size);
 
 #if defined(OS_POSIX)
 
 // Read exactly |bytes| bytes from file descriptor |fd|, storing the result
 // in |buffer|. This function is protected against EINTR and partial reads.
 // Returns true iff |bytes| bytes have been successfully read from |fd|.
 BASE_EXPORT bool ReadFromFD(int fd, char* buffer, size_t bytes);
 
 // Creates a symbolic link at |symlink| pointing to |target|.  Returns
 // false on failure.
 BASE_EXPORT bool CreateSymbolicLink(const FilePath& target,
                                     const FilePath& symlink);
 
 // Reads the given |symlink| and returns where it points to in |target|.
 // Returns false upon failure.
 BASE_EXPORT bool ReadSymbolicLink(const FilePath& symlink, FilePath* target);
 
-// Bits ans masks of the file permission.
+// Bits and masks of the file permission.
 enum FilePermissionBits {
   FILE_PERMISSION_MASK              = S_IRWXU | S_IRWXG | S_IRWXO,
   FILE_PERMISSION_USER_MASK         = S_IRWXU,
   FILE_PERMISSION_GROUP_MASK        = S_IRWXG,
   FILE_PERMISSION_OTHERS_MASK       = S_IRWXO,
 
   FILE_PERMISSION_READ_BY_USER      = S_IRUSR,
   FILE_PERMISSION_WRITE_BY_USER     = S_IWUSR,
   FILE_PERMISSION_EXECUTE_BY_USER   = S_IXUSR,
   FILE_PERMISSION_READ_BY_GROUP     = S_IRGRP,
@@ skipping 257 matching lines @@
 // This function simulates Move(), but unlike Move() it works across volumes.
 // This function is not transactional.
 BASE_EXPORT bool CopyAndDeleteDirectory(const FilePath& from_path,
                                         const FilePath& to_path);
 #endif  // defined(OS_WIN)
 
 }  // namespace internal
 }  // namespace base
 
 #endif  // BASE_FILE_UTIL_H_