Mac: Disable loading 2x bitmaps on 10.5 and 10.6

Mac: Disable loading 2x bitmaps on 10.5 and 10.6

Loading 2x bitmaps on 10.5 caused a regression in our startup time.

Since we don't need 2x bitmaps on 10.5 and 10.6 simple fix is to simply disable loading the bitmaps on those platforms.

BUG=80501
TEST=Ran on 10.6 and used logs to verify that the resource pak was not being loaded. Did the same on 10.7 and verified that the resource pak was being loaded.

[Robert Sesek, 2011-06-08 21:43:29]

LGTM

[commit-bot: I haz the power, 2011-06-08 22:36:43]

Change committed as 88426

[Mark Mentovai, 2011-06-09 14:30:50]

LGTM-post-facto

[Nico, 2012-06-18 15:27:50]

Err, what? We're happy with regressing 10.7 startup time just because we have no
bot which measures that?

[sail, 2012-06-18 19:32:46]

On 2012/06/18 15:27:50, Nico wrote:
> Err, what? We're happy with regressing 10.7 startup time just because we have
no
> bot which measures that?

I'm not sure what a good fix for this is. One solution would be to stop using
resource packs on Mac and load individual images. This way we can avoid loading
/ decoding the full image until necessary.

[Nico, 2012-06-18 19:59:32]

On 2012/06/18 19:32:46, sail wrote:
> On 2012/06/18 15:27:50, Nico wrote:
> > Err, what? We're happy with regressing 10.7 startup time just because we
have
> no
> > bot which measures that?
> 
> I'm not sure what a good fix for this is. One solution would be to stop using
> resource packs on Mac and load individual images. This way we can avoid
loading
> / decoding the full image until necessary.

Yes, NSImage can do lazy loading of reps. We should probably have something like
that.