In allocation grid show allocations as sorted by size only

At the moment we pretend that the rows are sorted by both size and count of allocations.

BUG=

Review URL: https://codereview.chromium.org/83183006

git-svn-id: svn://svn.chromium.org/blink/trunk@162560 bbb929c8-8fbe-4397-9dbb-9b2b20218538