Revert "Roll Clang r170392:r174491."

It turns out that r181918, which pinned the Clang revision on Mac ASan
bots worked a little too well, pinning the version on *all* Mac bots.

This reverts the Clang roll. We will then fix update.sh to get the Mac
ASan pinning correct, and then re-land the roll.

BUG=174873, 170629

Review URL: https://codereview.chromium.org/12256002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@182173 0039d316-1c4b-4281-b951-d872f2087c98
2 files changed