Mac: Keep groups when sorting task manager, like windows does.
Mac: Keep groups when sorting task manager, like windows does.

Also fix favicons in task manager.

BUG=32148
TEST=Have a few tabs that share a process. Sort of various columns in the task manager, the process group should stay one block.

Review URL: http://codereview.chromium.org/3029041

git-svn-id: de016e52bd170d2d4f2344f9bf92d50478b649e0@54206 0039d316-1c4b-4281-b951-d872f2087c98

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