Use permissions 0666 on POSIX platforms

Revert the hack introduced by http://crrev.com/290143005

BUG=409416

Review URL: https://codereview.chromium.org/1396613004

Cr-Commit-Position: refs/heads/master@{#353963}


CrOS-Libchrome-Original-Commit: 8a24d2b903636c83780281400aeba6164fdb358a
diff --git a/base/files/file_util_posix.cc b/base/files/file_util_posix.cc
index ffa79a4..eb8620d 100644
--- a/base/files/file_util_posix.cc
+++ b/base/files/file_util_posix.cc
@@ -674,7 +674,7 @@
 
 int WriteFile(const FilePath& filename, const char* data, int size) {
   ThreadRestrictions::AssertIOAllowed();
-  int fd = HANDLE_EINTR(creat(filename.value().c_str(), 0640));
+  int fd = HANDLE_EINTR(creat(filename.value().c_str(), 0666));
   if (fd < 0)
     return -1;