Added read-only file error test.

base/test/test_file_util_posix.cc

Index: base/test/test_file_util_posix.cc
diff --git a/base/test/test_file_util_posix.cc b/base/test/test_file_util_posix.cc
index 0096c9e815df5e3c723012cd5e73b555e176c063..4e28a24ac40277793ef89b3b61ce77bc282189fd 100644
--- a/base/test/test_file_util_posix.cc
+++ b/base/test/test_file_util_posix.cc
@@ -32,6 +32,43 @@ bool DenyFilePermission(const FilePath& path, mode_t permission) {
   return rv == 0;
 }
 
+// Gets a blob indicating the permission information for |path|.
+// |length| is the length of the blob.  Zero on failure.
+// Returns the blob pointer, or NULL on failure.
+void* GetPermissionInfo(const FilePath& path, size_t* length) {
+  DCHECK(length);
+  *length = 0;
+
+  struct stat stat_buf;
+  if (stat(path.value().c_str(), &stat_buf) != 0)
+    return NULL;
+
+  *length = sizeof(mode_t);
+  mode_t* mode = new mode_t;
+  *mode = stat_buf.st_mode & ~S_IFMT;  // Filter out file/path kind.
+
+  return mode;
+}
+
+// Restores the permission information for |path|, given the blob retrieved
+// using |GetPermissionInfo()|.
+// |info| is the pointer to the blob.
+// |length| is the length of the blob.
+// Either |info| or |length| may be NULL/0, in which case nothing happens.
+bool RestorePermissionInfo(const FilePath& path, void* info, size_t length) {
+  if (!info || (length == 0))
+    return false;
+
+  DCHECK_EQ(sizeof(mode_t), length);
+  mode_t* mode = reinterpret_cast<mode_t*>(info);
+
+  int rv = HANDLE_EINTR(chmod(path.value().c_str(), *mode));
+
+  delete mode;
+
+  return rv == 0;
+}
+
 }  // namespace
 
 bool DieFileDie(const FilePath& file, bool recurse) {
@@ -140,4 +177,16 @@ bool MakeFileUnwritable(const FilePath& path) {
   return DenyFilePermission(path, S_IWUSR | S_IWGRP | S_IWOTH);
 }
 
+PermissionRestorer::PermissionRestorer(const FilePath& path)
+    : path_(path), info_(NULL), length_(0) {
+  info_ = GetPermissionInfo(path_, &length_);
+  DCHECK(info_ != NULL);
+  DCHECK_NE(0u, length_);
+}
+
+PermissionRestorer::~PermissionRestorer() {
+  if (!RestorePermissionInfo(path_, info_, length_))
+    NOTREACHED();
+}
+
 }  // namespace file_util