GitLab

In this CL, we reuse hashset that control all the assigned slots
in the shadowroot for each node, added previous CL.
Thanks to the hashset we can find the assigned slot for each
node in O(1) order, instead of searching all the slot for each
shadow root when we call slot change event.

We will improve this implementation in another CL.

Result of perftests:
https://pinpoint-dot-chromeperf.appspot.com/job/151f9a47640000

Previous implementation CL: crrev.com/c/1179555

See design doc at
https://docs.google.com/document/d/1n2iDNkI5bF4B5eefxa0SRSyS_RVchvTNSqezvA4PyF4/edit?usp=sharing

Bug: 869308
Change-Id: I96fc4c50d9083eca199c7849db0097e73436983d
Reviewed-on: https://chromium-review.googlesource.com/1201513
Commit-Queue: Kyoko Muto <kymuto@google.com>
Reviewed-by: Hayato Ito <hayato@chromium.org>
Cr-Commit-Position: refs/heads/master@{#592785}