Fixes --output-format default case.

Fixes --output-format default case.

From python optparse docs for action='append':

"It also means that if the default value is non-empty, the default
elements will be present in the parsed value for the option, with any
values from the command line appended after those default values:"

So, to actually create a default, we have to set it later in
CreateResults. Unfortunate, but true. Thanks vogelheim@ for catching
this.

BUG=

Committed: https://crrev.com/ce5f7d429fde7fe62a83735658b54624b7077387
Cr-Commit-Position: refs/heads/master@{#295782}

[ariblue, 2014-09-19 17:45:45]

ariblue@google.com changed reviewers:
+ chrishenry@google.com, nednguyen@google.com

[chrishenry, 2014-09-19 19:04:47]

lgtm

Good to know.

[ariblue, 2014-09-19 19:16:10]

The CQ bit was checked by ariblue@google.com

[commit-bot: I haz the power, 2014-09-19 19:17:32]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/585023002/1

[commit-bot: I haz the power, 2014-09-19 21:25:01]

Committed patchset #1 (id:1) as e542870377fdcbcdf5e39c0aa9811d099355288d

[commit-bot: I haz the power, 2014-09-19 21:25:51]

Patchset 1 (id:??) landed as
https://crrev.com/ce5f7d429fde7fe62a83735658b54624b7077387
Cr-Commit-Position: refs/heads/master@{#295782}