[Coverity] Extension pointer can be null in the if clause, so we should rely on extension_id

Extension pointer can be null in the if clause, so we should rely on extension_id instead of extension->id().

BUG=None
CID=109059
TBR=yoz

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=221692

[Finnur, 2013-09-03 14:45:56]

Friendly ping.

[Gaurav, 2013-09-05 18:16:21]

On 2013/09/03 14:45:56, Finnur wrote:
> Friendly ping.

lgtm

[commit-bot: I haz the power, 2013-09-06 08:49:09]

No LGTM from a valid reviewer yet. Only full committers are accepted.
Even if an LGTM may have been provided, it was from a non-committer or
a lowly provisional committer, _not_ a full super star committer.
See http://www.chromium.org/getting-involved/become-a-committer
Note that this has nothing to do with OWNERS files.

[Finnur, 2013-09-06 08:58:18]

On 2013/09/06 08:49:09, I haz the power (commit-bot) wrote:
> No LGTM from a valid reviewer yet. Only full committers are accepted.
> Even if an LGTM may have been provided, it was from a non-committer or
> a lowly provisional committer, _not_ a full super star committer.
> See http://www.chromium.org/getting-involved/become-a-committer
> Note that this has nothing to do with OWNERS files.

It feels a little silly, asking for approval from a third-party (yoz) when the
original code submitter (grv) has given the green light and I'm in the OWNERS
chain, but that's what it is. I'll TBR this approval, since this is a trivial
change.

[commit-bot: I haz the power, 2013-09-06 08:59:34]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/finnur@chromium.org/23496030/1

[commit-bot: I haz the power, 2013-09-06 12:34:08]

Change committed as 221692