Use top-down and bottom-up profile notions in allocation profiler

Similar to the CPU profiler there are top-down and bottom up allocation profile views. Data structures are renamed to use correponding naming scheme.

BUG=277984
R=alph@chromium.org

Review URL: https://codereview.chromium.org/202953003

git-svn-id: svn://svn.chromium.org/blink/trunk@169432 bbb929c8-8fbe-4397-9dbb-9b2b20218538