Revert of mac: Switch the default build configuration to use the 10.10 SDK.

Revert of mac: Switch the default build configuration to use the 10.10 SDK. (patchset #2 id:20001 of https://codereview.chromium.org/1246743003/)

Reason for revert:
Causes gclient runhooks to fail on bots that don't have the 10.10 SDK (even though they don't need to compile)

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
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=463170
Committed: https://crrev.com/53e1ddcd0f7bd0934157e149903feb1893e9aac7
Cr-Commit-Position: refs/heads/master@{#341003}

[erikchen, 2015-07-29 22:39:50]

Created Revert of mac: Switch the default build configuration to use the 10.10
SDK.

[commit-bot: I haz the power, 2015-07-29 22:40:51]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1254123003/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1254123003/1

[commit-bot: I haz the power, 2015-07-29 22:42:40]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-07-29 22:43:17]

Patchset 1 (id:??) landed as
https://crrev.com/53e1ddcd0f7bd0934157e149903feb1893e9aac7
Cr-Commit-Position: refs/heads/master@{#341003}