Revert of Reland #1: Switch the default build configuration to use the 10.10 SDK.

Revert of Reland #1: Switch the default build configuration to use the 10.10 SDK. (patchset #1 id:1 of https://codereview.chromium.org/1257643005/)

Reason for revert:
I believe this is causing a lot of issues with layout, no idea why though.
https://code.google.com/p/chromium/issues/detail?id=515836

Original issue's description:
> Reland #1: Switch the default build configuration to use the 10.10 SDK.
>
> All known problems have been fixed since the first attempt to land this CL.
>
> Original issue's description:
> > mac: Switch the default build configuration to use the 10.10 SDK.
> >
> > This change is intended to be temporary. The goal is to release a Canary
> > compiled against the 10.10 SDK, and then to revert this CL.
> >
> > BUG=463170
> >
> > Committed: https://crrev.com/42ba22e0b8e87f758804537f64db23ff6438e451
> > Cr-Commit-Position: refs/heads/master@{#340992}
>
> TBR=thakis@chromium.org,amineer@chromium.org
> BUG=463170
>
> Committed: https://crrev.com/345c0cf47947f209e628941b38d76dca90aee49d
> Cr-Commit-Position: refs/heads/master@{#341261}

TBR=amineer@chromium.org,thakis@chromium.org,erikchen@chromium.org
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=463170
Committed: https://crrev.com/2f573334aa30d92dc04dd35fab41ed4658b87b36
Cr-Commit-Position: refs/heads/master@{#341306}

[dmurph, 2015-07-31 10:06:58]

Created Revert of Reland #1: Switch the default build configuration to use the
10.10 SDK.

[commit-bot: I haz the power, 2015-07-31 10:07:11]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1266603007/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1266603007/1

[commit-bot: I haz the power, 2015-07-31 10:07:55]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-07-31 10:08:39]

Patchset 1 (id:??) landed as
https://crrev.com/2f573334aa30d92dc04dd35fab41ed4658b87b36
Cr-Commit-Position: refs/heads/master@{#341306}

[Michael Achenbach, 2015-07-31 20:13:41]

Also note https://code.google.com/p/chromium/issues/detail?id=515824 and please
prepare the bot before relanding.