Pass empty email & password to ReadOnlyRietveld in dry run of commit queue

This avoids requiring real Rietveld credentials or specifying empty
user name on the command line (which is counterintuitive).

It also additionally ensures that nothing on Rietveld will change, even if there is a bug in ReadOnlyRietveld wrapper.

BUG=none

Review URL: https://codereview.chromium.org/145173004

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/commit-queue@246483 0039d316-1c4b-4281-b951-d872f2087c98
2 files changed