Revert 235863 "Remove blacklisting of Mac OS 10.6 and 10.7."

> Remove blacklisting of Mac OS 10.6 and 10.7.
> 
> Add blacklisting of VMWare driver on 10.7 because it hangs.
> 
> Disable compositing expectation test on 10.7 because it will
> give different results depending on whether it is running on
> a VM or real hardware.
> 
> Expand disabling of PhishingClassifierTest.DisableDetection because it
> flakes on all Mac versions now.
> 
> TBR=vangelis
> BUG=266186
> 
> Review URL: https://codereview.chromium.org/62333028

TBR=ccameron@chromium.org

Review URL: https://codereview.chromium.org/75513004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@235903 0039d316-1c4b-4281-b951-d872f2087c98
Adding 2 simple UMA stats to track shelf alignment usage, firstly track when a shelf alignment is changed (rare), and during usage of the shelf launcher (buttons on the shelf) track the current alignment (more common) to provide some data on how frequent usage is of the various alignments.

BUG=298174
TBR=askvitkine@chromium.org

Review URL: https://codereview.chromium.org/26373009

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@235904 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 235904