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

base/files/file_util_unittest.cc

Index: base/files/file_util_unittest.cc
diff --git a/base/files/file_util_unittest.cc b/base/files/file_util_unittest.cc
index 08c9587cc0655895e4604cc7e85be88f25215d05..e61cb89267feb3fe22dfafdc0098db1b82d211b4 100644
--- a/base/files/file_util_unittest.cc
+++ b/base/files/file_util_unittest.cc
@@ -2143,6 +2143,28 @@ TEST_F(FileUtilTest, TouchFile) {
             file_info.last_modified.ToInternalValue());
 }
 
+#if defined(OS_POSIX) && !defined(OS_ANDROID)
+TEST_F(FileUtilTest, WriteFileWithMode) {
+  FilePath data_dir =
+      temp_dir_.path().Append(FILE_PATH_LITERAL("FilePathTest"));
+
+  // Create a fresh, empty copy of this directory.
+  if (PathExists(data_dir)) {

[asanka, 2014/11/03 14:44:57]

This test, and the creation of a separate test directory should not be necessary
since it implies that temp_dir_ is not unique. The test fixture is supposed to
guarantee that it is unique per test. I.e. each individual test is given a
freshly constructed fixture including its own temp directory.

+    ASSERT_TRUE(DeleteFile(data_dir, true));
+  }
+  ASSERT_TRUE(CreateDirectory(data_dir));
+
+  FilePath foobar(data_dir.Append(FILE_PATH_LITERAL("foobar.txt")));
+  std::string data("hello");
+  mode_t mode = 0644;
+  ASSERT_TRUE(WriteFileWithMode(foobar, data.c_str(), data.length(), mode));
+
+  struct stat status;
+  ASSERT_EQ(0, stat(foobar.value().c_str(), &status));

[asanka, 2014/11/03 14:44:57]

Is there's a more aggressive umask on the MSan bots? If the umask is something
like 066, then we could end up with the results we are seeing. I can't tell for
sure without knowing what the configuration there is.

I agree with you that unless there's a memory access error or something, a test
that passes on the Linux bot should pass on the Linux MSan bot. But I also think
it might be best for the test to account for non-standard umasks, either by
explicitly setting a umask, or taking the umask into account.

This has to be done carefully, since if the test is not running in its own
process, then it is running in series with other tests. So we have to restore
the umask to its former glory before returning.

I prefer setting an explicit umask since otherwise the test wouldn't be testing
anything if the umask in effect is overly aggressive.

+  ASSERT_EQ(mode, status.st_mode & 0777);
+}
+#endif
+
 TEST_F(FileUtilTest, IsDirectoryEmpty) {
   FilePath empty_dir = temp_dir_.path().Append(FILE_PATH_LITERAL("EmptyDir"));