metrics: Update UpdateEngineErrorCode enumeration.
Add three more error codes recently added to the ChromeOS update_engine.
I've seen at least value 43 in the wild but also add 44 and 45 as
these errors may be reported in the future.
BUG=chromium:355745
TEST=Validated the xml, pretty print succeeded.
R=asvitkine@chromium.org, avakulenko@chromium.org, deymo@chromium.org, isherman@chromium.org, jar@chromium.org, sosa@chromium.org
NOTRY=true
Review URL: https://codereview.chromium.org/
218683012
git-svn-id: svn://svn.chromium.org/chrome/trunk/src@261100 0039d316-1c4b-4281-b951-d872f2087c98