[DevTools] Unflake .../sources/debugger/debugger-uncaught-promise-on-pause.html
[DevTools] Unflake .../sources/debugger/debugger-uncaught-promise-on-pause.html

BUG=572723
TBR=dgozman@chromium.org
NOTRY=true

Review URL: https://codereview.chromium.org/1882743002

Cr-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#386891}

axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk