[GN]: Fix typo in roll_deps.py

[GN]: Fix typo and a bug in the GN roll script.

When complete, the script attempts to switch from the branches it creates
to build and roll things back to the branch you were on before.

The way it determines what branch you were on before is by looking at
git's reflog. However, the way I was looking at the reflog was wrong;
first, it was doing an re.match() instead of an re.search(), and so
it was looking for a match at the beginning of the output (which would
never be true). Second, we were looking at only the most recent entry,
and when the roll script actually executed, the most recent entry would
always be a commit, not a checkout, and so we wouldn't see what the
previous branch was.

BUG=none
R=dpranke@chromium.org

Committed: https://crrev.com/c9ef0df1e21a0e9be8c855fbbf01386ed0617d2a
Cr-Commit-Position: refs/heads/master@{#351613}

[Dirk Pranke, 2015-09-30 18:17:43]

lgtm.

yay testing! :).

[Dirk Pranke, 2015-09-30 18:18:54]

On 2015/09/30 18:17:43, Dirk Pranke wrote:
> lgtm.
> 
> yay testing! :).

Oh, can you merge in https://codereview.chromium.org/1376583003/ ? That way I
won't have to do
a merge, and we really need both sets of fixes anyway.

[Bons, 2015-09-30 18:19:16]

The CQ bit was checked by andybons@chromium.org

[Bons, 2015-09-30 18:20:55]

On 2015/09/30 18:18:54, Dirk Pranke wrote:
> On 2015/09/30 18:17:43, Dirk Pranke wrote:
> > lgtm.
> > 
> > yay testing! :).
> 
> Oh, can you merge in https://codereview.chromium.org/1376583003/ ? That way I
> won't have to do
> a merge, and we really need both sets of fixes anyway.

Sure.

[Bons, 2015-09-30 18:20:58]

The CQ bit was unchecked by andybons@chromium.org

[Bons, 2015-09-30 18:26:52]

On 2015/09/30 18:20:55, Bons wrote:
> On 2015/09/30 18:18:54, Dirk Pranke wrote:
> > On 2015/09/30 18:17:43, Dirk Pranke wrote:
> > > lgtm.
> > > 
> > > yay testing! :).
> > 
> > Oh, can you merge in https://codereview.chromium.org/1376583003/ ? That way
I
> > won't have to do
> > a merge, and we really need both sets of fixes anyway.
> 
> Sure.

Merged in. Will close your patch.

[Bons, 2015-09-30 18:27:01]

The CQ bit was checked by andybons@chromium.org

[Bons, 2015-09-30 18:27:01]

The patchset sent to the CQ was uploaded after l-g-t-m from dpranke@chromium.org
Link to the patchset: https://codereview.chromium.org/1381753003/#ps40001
(title: "merge in dirk's patch")

[Dirk Pranke, 2015-09-30 18:28:48]

lgtm, thanks.

[commit-bot: I haz the power, 2015-09-30 18:35:41]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1381753003/40001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1381753003/40001

[commit-bot: I haz the power, 2015-09-30 19:01:45]

Committed patchset #3 (id:40001)

[commit-bot: I haz the power, 2015-09-30 19:02:35]

Patchset 3 (id:??) landed as
https://crrev.com/c9ef0df1e21a0e9be8c855fbbf01386ed0617d2a
Cr-Commit-Position: refs/heads/master@{#351613}