Unflake inspector/sources/debugger/async-callstack-in-console.html

BUG=392531
TBR=yurys

Review URL: https://codereview.chromium.org/378293006

git-svn-id: svn://svn.chromium.org/blink/trunk@177807 bbb929c8-8fbe-4397-9dbb-9b2b20218538