sheriffbot roll-chromium-deps shouldn't create a bug with None as the new revision.
https://bugs.webkit.org/show_bug.cgi?id=73482

Patch by Alan Cutter <alancutter@chromium.org> on 2013-03-06
Reviewed by Ryosuke Niwa.

Added input checking to the UpdateChromiumDEPS step.
Removed the default use of LKGR when the revision input is invalid. "LKGR" must be explicitly given instead.

* Scripts/webkitpy/tool/bot/irc_command.py: Updated input validation and error message handling.
(RollChromiumDEPS):
(RollChromiumDEPS._parse_args):
(RollChromiumDEPS.execute):
* Scripts/webkitpy/tool/bot/irc_command_unittest.py: Updated unit tests.
(IRCCommandTest.test_roll_chromium_deps):
* Scripts/webkitpy/tool/bot/ircbot_unittest.py: Updated unit tests.
(IRCBotTest.test_roll_chromium_deps_to_lkgr):
* Scripts/webkitpy/tool/commands/roll_unittest.py: Updated unit tests.
* Scripts/webkitpy/tool/steps/updatechromiumdeps.py: Added input validation and added new error handling cases. Changed the logic of deciding to use LKGR to be only when the input is "LKGR".
(UpdateChromiumDEPS._fetch_last_known_good_revision):
(UpdateChromiumDEPS):
(UpdateChromiumDEPS._parse_revision_number):
(UpdateChromiumDEPS._validate_revisions):
(UpdateChromiumDEPS.run):
* Scripts/webkitpy/tool/steps/updatechromiumdeps_unittest.py: Added unit tests.
(UpdateChromiumDEPSTest):
(UpdateChromiumDEPSTest.test_parse_revision_number):
* Scripts/webkitpy/tool/commands/roll.py: Updated help text.
(RollChromiumDEPS):
(PostChromiumDEPSRoll):

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@144940 268f45cc-cd09-0410-ab3c-d52691b4dbfc