[system-health] Wait for 10 seconds after each story (except for memory benchmarks)

Non-memory SH benchmarks:
All SH stories will wait for 10 seconds after loading.

Memory SH benchmarks:
All SH stories will re-use action_runner.MeasureMemory().

BUG=589726,637158
CQ_INCLUDE_TRYBOTS=master.tryserver.chromium.perf:android_s5_perf_cq;master.tryserver.chromium.perf:linux_perf_cq;master.tryserver.chromium.perf:mac_retina_perf_cq;master.tryserver.chromium.perf:winx64_10_perf_cq

Review-Url: https://codereview.chromium.org/2248693002
Cr-Commit-Position: refs/heads/master@{#413128}
1 file changed