Add external extensions json source in proper mac location.

base/file_util.h

Index: base/file_util.h
diff --git a/base/file_util.h b/base/file_util.h
index cd7fa9fafcbe68865e578b3c173adb84419e34e7..4a53fbf392f344c25ba0bfde51bfe43f7ab57427 100644
--- a/base/file_util.h
+++ b/base/file_util.h
@@ -659,6 +659,28 @@ enum FileSystemType {
 BASE_EXPORT bool GetFileSystemType(const FilePath& path, FileSystemType* type);
 #endif
 
+#if defined(OS_POSIX)
+// Test that |path| can only be changed by a specific user and group.
+// Specifically, test that all parts of |path| under (and including) |base|:
+// * Exist.
+// * Are owned by a specific user and group.

[Evan Martin, 2011/08/30 17:26:38]

Does it matter that you check the group, when you don't check whether it's
group-modifiable?

[Sam Kerner (Chrome), 2011/09/16 18:12:59]

I considered not checking group membership if the group can't write.  I chose
not to do this, because there is no legitimate reason any group other than admin
should own /Library/... paths on mac os, and admin can write to everything under
/Library/.  If some future user needs it we could add it, but loosening the test
makes it more complex, and it will not be exercised outside unit tests.

+// * Are not writable by all users.
+// * Are not symbolic links.
+// This is useful for checking that a config file is administrator-controlled.
+// |base| must contain |path|.
+BASE_EXPORT bool IsPathControlledByUser(const FilePath& base,
+                                        const FilePath& path,
+                                        uid_t owner_uid,
+                                        gid_t group_gid);
+
+// Is |path| writable only by a user with administrator privileges?
+// Check this by testing that |path|, and every parent directory including
+// the root of the filesystem, are owned by root, controlled by the group
+// "admin", are not writable by all users, and contain no symbolic links.

[Evan Martin, 2011/08/30 17:26:38]

What is "admin" here?  It is not true that my root directory is controlled by
that user.

[Sam Kerner (Chrome), 2011/09/16 18:12:59]

Updated to make it clear that this function is mac-specific.  Put it in #if
defined(OS_MACOSX).

+// Will return false if |path| does not exist.
+BASE_EXPORT bool IsPathControlledByAdmin(const FilePath& path);
+#endif  // defined(OS_POSIX)
+
 }  // namespace file_util
 
 // Deprecated functions have been moved to this separate header file,