perf: Add more tough ad cases

perf: Add more tough ad cases

This patch adds a bunch of pages with challenging ads and analytics
content to the smoothness.tough_ad_cases benchmark. This set includes
real world web sites and a synthetic page with 5 Swiffy ads on it.

These pages also try to use a more realistic interaction model:

1. Instead of waiting for the page to load fully, try scrolling
roughly 1 second after loading. This helps to catch more jank
during loading.

2. Scroll multiple times instead of just once. This invokes any
Javascript touch handlers multiple times and helps to measure
their contribution to jank.

BUG=487937,510398,500962,496791,447731,395245,515517
CQ_EXTRA_TRYBOTS=tryserver.chromium.perf:linux_perf_bisect;tryserver.chromium.perf:mac_perf_bisect;tryserver.chromium.perf:win_perf_bisect;tryserver.chromium.perf:android_nexus5_perf_bisect

Review URL: https://codereview.chromium.org/1252243003

Cr-Commit-Position: refs/heads/master@{#342118}