Revert 253993 "Default to VS2013 on Windows"

Checking whether this caused several hundred Win 7 layout test image diffs.

> Default to VS2013 on Windows
> 
> This switches the default toolchain on Windows to VS2013.
> 
> TBR=cpu@chromium.org
> BUG=323300,309197
> 
> Review URL: https://codereview.chromium.org/178263005

TBR=scottmg@chromium.org

Review URL: https://codereview.chromium.org/183993005

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@254038 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 254038