Rename |imp| => |impl| in wtf (one use)

Rename |imp| => |impl| in wtf (one use)

This is the last inconsistent use of |imp| instead of |impl| in Chromium C++.
(There are a few Objective C++ uses that I'm not touching.)

Followup to
Rename |imp| => |impl| in bindings generation
https://codereview.chromium.org/202203009/

TBR=abarth

Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=169415

[Nils Barth (inactive), 2014-03-18 05:03:14]

Clean-up.

[Nils Barth (inactive), 2014-03-18 05:03:20]

The CQ bit was checked by nbarth@chromium.org

[commit-bot: I haz the power, 2014-03-18 05:03:25]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/nbarth@chromium.org/203073002/1

[commit-bot: I haz the power, 2014-03-18 06:07:03]

Change committed as 169415

[haraken, 2014-03-18 06:36:33]

LGTM (but I'm not an OWNER of wtf/)

[Nils Barth (inactive), 2014-03-19 01:42:45]

abarth: TBR?

[abarth-chromium, 2014-03-19 17:05:47]

LGTM :)