Allow POSIX callers to specify a new file's mode.

base/files/file_util_posix.cc

Index: base/files/file_util_posix.cc
diff --git a/base/files/file_util_posix.cc b/base/files/file_util_posix.cc
index 5a94cef661319e39b98ea10037113371b4a2d2ac..7bbdfc5b7c35f2266b3f0819ff1700ca331e9241 100644
--- a/base/files/file_util_posix.cc
+++ b/base/files/file_util_posix.cc
@@ -693,6 +693,15 @@ int WriteFile(const FilePath& filename, const char* data, int size) {
   return bytes_written;
 }
 
+bool WriteFileWithMode(const FilePath& filename, const char* data, int size,
+                       mode_t mode) {
+  ThreadRestrictions::AssertIOAllowed();
+  ScopedFD file(HANDLE_EINTR(creat(filename.value().c_str(), mode)));
+  if (!file.is_valid())
+    return false;
+  return WriteFileDescriptor(file.get(), data, size);
+}
+
 bool WriteFileDescriptor(const int fd, const char* data, int size) {
   // Allow for partial writes.
   ssize_t bytes_written_total = 0;