DevTools: Fix base snapshot selector combobox in heap profiler.

BUG=343465
R=loislo@chromium.org

Review URL: https://codereview.chromium.org/163373002

git-svn-id: svn://svn.chromium.org/blink/trunk@167084 bbb929c8-8fbe-4397-9dbb-9b2b20218538