dbus: Add comments about the right way to expose methods

Along the way, fix the order in the test service used in unit tests.

BUG=332120
TEST=dbus_unittests pass as before

Review URL: https://codereview.chromium.org/125673003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@243770 0039d316-1c4b-4281-b951-d872f2087c98
Implement lstat by stat in nacl_io

As nacl_io does not support

TEST=./build_tools/build_sdk.py
TEST=./build_tools/test_sdk.py

Review URL: https://codereview.chromium.org/125693002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@243771 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 243771