Remove .dmg from the list of dangerous file extensions for Mac OS X.

Remove .dmg from the list of dangerous file extensions for Mac OS X.

While here, add some that are dangerous.

BUG=29287, 19096
TEST=When downloading .bash, .command, .csh, .ksh, .sh, .tcsh files,
expect the "The file may harm your computer" warning.
Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=158470

[Chris Palmer, 2012-09-13 23:36:38]

In http://code.google.com/p/chromium/issues/detail?id=19096#c26, stuartmorgan
suggests using an empty list of dangerous downloads, falling back on the
platform's warnings. I could go either way; no matter what, though, this list
needs updating.

[Nico, 2012-09-14 00:38:08]

lgtm

fine with me

[Randy Smith (Not in Mondays), 2012-09-14 12:52:58]

Happy to go with your judgement on this.  

LGTM.

[Randy Smith (Not in Mondays), 2012-09-14 15:21:50]

On 2012/09/14 12:52:58, rdsmith wrote:
> Happy to go with your judgement on this.  
> 
> LGTM.

I just added a note to 29287 expressing concern about IDME (== downloading
arbitrary files with a mouse click from the user).  I'm still happy to go with
your judgement, just wanted to make sure your judgement included that concern as
input.

[palmer, 2012-09-14 21:19:02]

> I just added a note to 29287 expressing concern about IDME (== downloading
> arbitrary files with a mouse click from the user).  I'm still happy to go with
> your judgement, just wanted to make sure your judgement included that concern
as
> input.

Yes, I just added a note there saying that I could not get IDME to work as
documented. It would bother me somewhat, if I could get it to work...

[stuartmorgan, 2012-09-17 05:44:08]

LGTM

We may want to move to:

#elif defined(OS_POSIX)
<lots of stuff>
#if !defined(OS_MACOSX)
<a few more things>
#endif
#endif

at some point to remove duplication, if the list gets long, but for now it's not
a big deal.

[commit-bot: I haz the power, 2012-09-24 20:45:18]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/palmer@chromium.org/10933082/1

[commit-bot: I haz the power, 2012-09-24 23:29:06]

Sorry for I got bad news for ya.
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