[Mac] Chrome print dialog disregards system cancel key-command.

[Mac] Chrome print dialog disregards system cancel key-command.

Add support for Cmd- (the universal "cancel" shortcut on Mac) to close print dialog.

BUG=249786
R=dpapad@chromium.org

TEST=
1. Open a web page
2. Hit Cmd-P to bring up print dialog.
3. Hit Cmd- and observe.
4. The print dialog should get closed.

Committed: https://crrev.com/4b0e06faa400dcb73275098d17d2c523e7625fd6
Cr-Commit-Position: refs/heads/master@{#294142}

[Gaja, 2014-09-09 08:53:27]

PTAL.

[Lei Zhang, 2014-09-09 19:45:42]

thestig@chromium.org changed reviewers:
+ alekseys@chromium.org, thestig@chromium.org

[Lei Zhang, 2014-09-09 19:45:43]

+alekseys

[Aleksey Shlyapnikov, 2014-09-09 20:45:22]

lgtm

[Gaja, 2014-09-10 02:29:00]

The CQ bit was checked by gajendra.n@samsung.com

[commit-bot: I haz the power, 2014-09-10 02:41:14]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/gajendra.n@samsung.com/555733003/1

[commit-bot: I haz the power, 2014-09-10 02:41:16]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2014-09-10 02:41:16]

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 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.

[Lei Zhang, 2014-09-10 06:47:56]

lgtm stamp

[Lei Zhang, 2014-09-10 06:48:00]

The CQ bit was checked by thestig@chromium.org

[Gaja, 2014-09-10 06:52:15]

On 2014/09/10 06:47:56, Lei Zhang wrote:
> lgtm stamp

@Aleksey Shlyapnikov
@Lei Zhang	

Thanks!. 
Can I check Commit now? or should I wait for LGTM from dpapad?

[commit-bot: I haz the power, 2014-09-10 06:58:40]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/gajendra.n@samsung.com/555733003/1

[commit-bot: I haz the power, 2014-09-10 08:12:06]

Committed patchset #1 (id:1) as 4fbcfe02319e4b872c691e7424c309224a5a7d27

[commit-bot: I haz the power, 2014-09-10 10:56:03]

Patchset 1 (id:??) landed as
https://crrev.com/4b0e06faa400dcb73275098d17d2c523e7625fd6
Cr-Commit-Position: refs/heads/master@{#294142}