DevTools: Fix canvas profiler replay image positioning.

This was broken after moving split views to flex.

R=pfeldman, vsevik

Review URL: https://codereview.chromium.org/105843005

git-svn-id: svn://svn.chromium.org/blink/trunk@163279 bbb929c8-8fbe-4397-9dbb-9b2b20218538