HeapProfiler: fix regression in Performance tests suit.

_updateTransferProgress was moved to a separate transferHandler class.

BUG=none
R=yurys@chromium.org

Review URL: https://codereview.chromium.org/26568003

git-svn-id: svn://svn.chromium.org/blink/trunk@159573 bbb929c8-8fbe-4397-9dbb-9b2b20218538